Epoxy School Blog

Epoxy application - solventless epoxies and cold temperatures

When the cooler months roll around and temperatures drop, application can start to become a bit of a headache for contractors.

As a manufacturer of solventless epoxies, I can always bank on being asked two questions during these periods – 

  1. How can I make solventless epoxies easier to apply? 
  2. How can I speed up the cure? 

Obviously the answers can depend on the products being used, but there are a couple of things that help regardless.

Cold temperatures and epoxy handling

Firstly, let's take a look at making epoxy handling easier.

Step one involves getting the product out of the bucket and in single digit temperatures (1-10oC/34-50oF) the thick viscosity can make that a task in itself. With this in mind, storing the product on the floor in a cold shed is not going to help your cause. Instead, look to store the product in a warmer space, somewhere indoors away from the extremes and closer to 25oC/77oF. It doesn't have to be in your bed, although that would be perfect!

Keeping the product at moderate temperatures this way will also stop the products from turning into a gluggy semi-solid, which can happen with some epoxies in cold temperatures. Crystallisation, as it’s known, can be reversed by slowly heating and stirring the product, however you certainly don’t want to be doing that every time!

If storage at a reasonable temperature isn’t possible, some contractors make special “hot boxes” to warm the epoxy directly before use. These devices are essentially timber boxes that house a few kits of product and are heated via an electric fan-forced heater. There are also submersible heaters available that can keep certain volumes at a constant temperature, however I’m not too sure how practical they are in the field.

An example of a hot box used to warm epoxies before application in cold temperatures.

Cold temperatures and epoxy application

These little tricks might work well for getting the product up to a nice mixing temperature before use, but even that may not help you if the slab itself is extremely cold. A cold slab will tend to act like a big heat sink and this means even if your pre-heated product is 30oC/86oF when it hits the floor, it’ll quickly drop to the temperature of the slab once applied and drag you back to square one.

This cold substrate issue can be eased by heating the room, however if you're using a gas heater and your epoxy has a problem with amine blushing you’ll need to be extra careful. These heaters increase the levels of carbon dioxide when operating, which is one of the key ingredients needed for blushing to occur. This warning can actually be extended to any heater that doesn’t burn clean and therefore could potentially interfere with the flooring, e.g. kerosene heaters have been linked to adhesion problems.

Apart from heating, there’s also a school of thought out there that suggests using a thin epoxy to seal the surface first can make epoxy application easier because it protects the thicker basecoat from the icy slab. Such an approach may be worth trying if you can work in the additional cost and time of an extra coat.

Cool temperature and accelerating cure

Finally, cold temperatures also mean slower reaction times. If your epoxy isn’t adversely affected by heating as already discussed then continuing to heat the room after application can be a good way to achieve a shorter turnaround. Besides that, the answer to speeding things up is the use of a stir-in epoxy accelerator. Be aware these additives can affect the UV and chemical resistance of the product, so never use them in quantities greater than recommended and never in the final coat if possible.

I’ll finish off by adding that introducing a small amount of solvent to a solventless epoxy is also a popular way of reducing viscosity and making epoxy application easier. Unlike the other options given here, however, adding solvents won’t cut cure times in cool conditions and some solvents like acetone will drag it out even further!

Take care and talk to you later,


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Epoxy troubleshooting - concrete additives and coating adhesion

Like most people I suspect, there was a time when I thought concrete was just concrete and all slabs were the same. How wrong I was!

With a little more experience under my belt, I know how flawed this thinking is; in fact, I would now go as far as to say that NO two concrete slabs are exactly the same. It might sound like a big statement, but when you consider all the variables of modern concreting practices, it’s quite possible that even the same batch can end up looking and performing differently if applied in two separate locations.

Concrete slabs aren’t concrete slabs!

Why is this so? When you talk about different locations, you’re also talking about the potential for different weather (temperature, humidity, wind, sun light), different handling, different application, different finishing etc. All of these factors can have a big say in characteristics of a concrete slab and we haven’t even touched on the content of the concrete itself. Water and the aggregate composition are obvious variables here, but concrete has come a long way and these days all sorts of concrete additives can be used to speed up, slow down, harden and even slow corrosion depending on job demands. Imagining every slab as at least slightly different perhaps doesn’t seem so absurd after all!

Ok, concrete is ever-changing and unpredictable, so what? Well, for coating contractors it can actually be a bit of a problem because it challenges the age-old assumption that sticking to concrete is a sure thing. Some modifications can indeed interfere with coating adhesion and it was something I learnt the hard way several years ago.

The concrete additives lesson

The painful, yet extremely valuable lesson came through on a project involving a tilt slab construction coated with epoxy for protection and waterproofing.

For those unfamiliar with tilt slabs, these are slabs that are poured horizontally in moulds then cracked and erected to form the walls of whatever building is being constructed. A "mould release" is used to make it easier for concrete to break away and is generally added in controlled amounts to the moulds themselves and in between the concrete layers.

On this particular project however, there was a rush on the high-profile job (which happens more often than not these days) and the construction company needed the slabs to cure quicker. Conventional concrete accelerators were ruled out because the slabs were being poured on top of each other, so they figured the next best thing was to use greater quantities of mould release to allow successive pours to be done sooner.

Unfortunately, as it was later discovered, the excess mould release was absorbed by the slabs as they cured – not a problem if the panels were left as is, but a major snag when you plan to put a coating on them!

Because of the extreme levels of mould release used, the normal tilt wash detergents were no longer effective. They seemed to be doing their job on the surface, however the stuff that had soaked into the concrete was playing havoc with coating adhesion. After some desperate scrambling and frantic tensile adhesion tests, the solution ended up being multiple washes with the detergent and a deep grind to remove several millimetres of contaminated concrete before coating adhesion was restored. It was an intense experience and a huge sigh of relief was breathed by all I can tell you!

Samples of epoxy showing the difference in coating adhesion on concrete contaminated with mould release.

Be wary of concrete assumptions

I think the take-home message from this near disaster is you need to be wary of all concrete slabs, not just tilt slabs. Every slab is different and you need to ask questions of what you see before you rather than make assumptions. What is the composition of the slab? What else may have been added? What could it have been exposed to?

A similar scenario to the one above that I know catches many people out happens in residential garages. Instead of mould release, the contaminants in this case are the tyre shine products that are usually a type of silicon spray. Being invisible to the naked eye, it’s very easy to assume the concrete is clean and washing isn’t necessary. They give the floor a light grind and think it’s all gone well; only to watch in dismay a short time later as their beautiful new garage floor quickly peels off (read the post on Hot Tyre Pick-up).

Take care and talk to you later,


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Epoxy troubleshooting - hydrostatic pressure and moisture tolerance

What is hydrostatic pressure and how is it related to moisture tolerance?

If you’re a regular visitor to this blog, you would’ve previously read about the benefits of choosing moisture tolerant epoxy hardeners when it comes to avoiding amine blush (Epoxy troubleshooting – amine blush).

But, does a moisture tolerant product mean I don’t have to be concerned by hydrostatic pressure? I’ve heard these terms creep into the same conversation many times and feel as though it could end up down a dangerous path if one starts getting confused as the answer to the other. The answer is: no, they are two different issues really.

The difference between hydrostatic pressure and moisture tolerance

Hydrostatic pressure is arguably the most complex, poorly understood of all preparation issues and a great example of why flooring can be a tough gig. Not only is the issue itself a bit of a mystery, there also seems to be vagueness around the products used to fix it, and, as we’re highlighting here, some related concepts such as moisture tolerance.

In brief, being moisture tolerant means the product doesn’t react badly to moisture during application, which is a very handy property because you typically don’t have to worry about humidity in the air etc.

Hydrostatic pressure, on the other hand, is a powerful, destructive force that acts on a coating through the movement of water or water vapour in the slab. Typically this pressure is caused by a moisture source close to the bottom of the slab, which, in the absence of an effective moisture barrier below, sees water rise through the pores in the concrete. This migration becomes a problem in a coating sense when it becomes trapped beneath an impermeable film sitting on the surface, at which point the build up of pressure can be sufficient to blow sections off or cause other forms of damage like blisters.

You can probably see the relationship between moisture tolerance and hydrostatic pressure more clearly now; a moisture tolerant product might be able to handle application onto a slab with excess moisture, however this capability certainly doesn’t mean it will be safe from the hydrostatic pressure acting on it once it hardens.

Hydrostatic pressure affecting concrete in a basement.

Hydrostatic pressure warning signs

If moisture tolerant products aren’t the answer to hydrostatic pressure, what is? Before we get into that, let’s take a look at how you can diagnose such problems in the first place. Luckily, there are a few simple tests that can be used to spot hydrostatic pressure issues before you go and put a coating down.

To start with, grinding a spot and seeing what colour it turns can be quite informative. If it starts to darken soon after, this is a classic warning sign that hydrostatic forces are at play. In this case you should also keep an eye out for efflorescence, which are visible marks that result from water coming to the surface and depositing silt-like substances as it dries.

A step up on those basic visual tests is to tape a 60cm x 60cm/2ft x 2ft plastic sheet to the concrete with duct tape and leave it for 24 hours. If water droplets appear on the underside of the plastic, or if the concrete appears darker in this area, your slab could have a problem.

For those after a more scientific approach, moisture meters can also be purchased to measure the levels at points on a slab and alert you to any potential problems. With this equipment, most people talk about 5-6% as being the maximum acceptable moisture content of concrete for flooring before hydrostatic issues are raised.

Personally, I’d never count on just one of these when assessing a slab. I’d look for multiple signs of a problem first and use that to guide my judgement on any action that needs to be taken.

Dealing with hydrostatic pressure

If your checks all point in the same direction and you do have a hydrostatic pressure issue, there are two common ways of dealing with it – both of which look to create some form of water barrier to block it as it moves up through the slab.

Water-based epoxies are the first and probably the most common option here. These are typically 40-50% solids products that are applied onto a pre-wet slab. As the epoxy is water-based, it thins down very quickly and penetrates deeply before crosslinking to form a barrier. Other than that, there are also some colloidal silicate solutions that promote the ability to penetrate into the slab, reacting with the residual lime and cement to form a gel barrier instead.

A couple of quick side notes about these treatments – 

  1. Be careful when dealing with cracks as they may not consistently close off with these moisture barriers
  2. In basements or other below-grade spaces, hydrostatic pressure can also be an issue on the walls and should be dealt with in the same way if they’re to be coated.

In closing, I just wanted to make the point this post should only be taken as a broad overview to raise awareness of hydrostatic pressure and how it relates to moisture tolerance. As mentioned previously, hydrostatic pressure is a very technical, complex issue and further reading is recommended for a full understanding.

Take care and talk to you later,


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Surface preparation - can I sand concrete?

Is sanding an option for preparing new concrete slabs? I guess so, but not if you want the coating to stick!

This is very much “Floor Preparation 101” and I don’t want to spend too much time on it, but I still hear of contractors using coarse sandpaper on a Polivac machine to prepare new slabs and thought I’d explain why it’s not a great idea once and for all.

(Note: For those unfamiliar with the term, Polivac is a particular brand of machines used for buffing and sanding.)

Sanding concrete doesn't remove laitance

I think this bad habit can creep in when contractors come across a fresh, clean slab and underestimate the work that still needs to be done to make a coating stick. The slab might be brand new and a quick sand may seem good enough, but the problem with doing that is it fails to remove all the laitance and that means you can be headed for big trouble. The fact is sanding in this manner might only remove around 5-10% of the stuff sitting on top, which means the coating will floating on a bed of weak powder rather than anchored to a solid surface. It won’t be bonded well and will probably peel off as soon as it’s put under any stress, such as a car parked on top of it.

While preparing a new slab is generally a much easier task than a damaged, contaminated slab, you still need to do it properly. In most cases, this all boils down to laitance and getting the job done there. If you don’t, expect a call to come back and fix it!

A Polivac machine with sandpaper is not the right machine to prepare concrete.

When can I use a Polivac?

While using sandpaper on a Polivac doesn’t adequately remove laitance, you can get attachments that do the job well. As I mentioned in a previous post, Decorative epoxies – the polished concrete and warehouse looks, an example of this type of thing is something called Diamabrush, which uses diamonds on flexible brushes to prepare the concrete. As discussed in that post, it’s actually a good option for decorative resin flooring because it follows the contours of the slab rather than flatten it completely and that can have a number of advantages in that field.

Like I said, this topic is well documented and I didn’t want to go too far in this particular post. I simply wanted to highlight this common problem once again and ensure that you don’t feel tempted to sand the floor. There are many ways to remove laitance, however sanding is NOT one of them.

Take care and talk to you later,


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Epoxy application - can epoxies be applied over tiles?

Contractors working in the residential, retail and commercial fields are almost guaranteed to hear one question from your customers: “Can you go over tiles?”

It’s a very important question to be able to answer and I think it will only become more important as the resin flooring market continues to grow. While tiles have always been a popular flooring choice, I believe more and more people are falling in love with the seamless finish epoxy floors provide and they’re starting to look into their options more seriously.

With so many tiled floors already out there, a big part of this process from the customer’s point of view is trying to understand how to make the switch painlessly. Most people realise that removing tiles can be a messy, time consuming job – not to mention costly if it involves raising the floor by up to 15mm/6” afterwards – and they’re naturally drawn to the idea of simply going over the top; hence the popular question.

So, can epoxies go over floor tiles? I think many contractors will know the simple answer is yes, however it doesn’t always mean they should. There are some conditions and additional thoughts I always consider before jumping in. Here are a few of them.

Sticking to tiles

When going over the top of a tiled floor, the main concern is adhesion – with epoxy onto the tile and tile onto concrete.

Some floor tiles have a glossy finish from the glazing process, which can make them tricky to bond to. If the tiles are glazed, the gloss will need to be removed by grinding to allow the epoxy to grab hold. You can look to micro-etch with acid-based etchers, but in my experience this kind of preparation can be hit and miss. Vitrified tiles are non-porous and extremely hard all the way through, so grinding alone may not be enough to get a strong bond. With these, a specialist primer is typically needed to make it stick.

A glossy finish can also be a result of a sealer on the tiles, e.g. lots of terracotta tiles aren’t glazed, but a sealer can sometimes be applied to prevent them from looking dirty or showing a spill. If the tile is sealed then you’ll also need to grind as these sealers often have hydrophobic properties and can be troublesome if you approach them like a normal coating.

In addition to glaze and gloss of the tile itself, I always pay close attention to the condition of the grout lines. The biggest concern here is contamination. Being a porous material, grout has a nasty habit of soaking up all sorts of grease and grime that can play havoc with epoxy adhesion. If the tiled floor is in a commercial kitchen or anywhere else exposed to heavy oil contamination, you may find yourself digging up the grout lines or removing everything just to be safe.

Finally, as already mentioned, the issue of adhesion must also be considered with respect to the quality of the bond between floor tile and concrete. Tiles can become “drummy” over time and that represents a weak point in the flooring. If more than a few tiles are found to be loose during inspection – or they start to shatter, crack or pop while grinding – it’s probably better to remove them all so the concrete underneath can be used instead. If they all feel fine and you end up going over them, I’d recommend just having a word to the client anyway to make it clear you can’t control what the tiles may do in the future.

Getting the tiles flat

If you’re confident the tiled floor is clean and sound and you can stick to them with your epoxy, the next challenge is to get them flat. In my experience, there aren’t too many clients fond of protruding edges or visible grout lines in their new resin floor.

While a flat substrate can be achieve mechanically through grinding, it’s generally quicker and easier to apply a levelling compound to do the job. There are a few things I’ll say about this task.

Firstly, you may need to apply up to 5mm/2” to cover grout lines fully, which can add significant cost to the project and cause problems elsewhere with regards to heights around fixtures etc. These aren’t major problems for the contractor per se, however it can be if these things are communicated clearly to the client beforehand.

Secondly, don’t fall into the trap of thinking all levelling compounds are the same. While they may produce a flat surface, different products can interfere with the flooring system on top in different ways and give some undesirable results. For instance, floor levellers heavily diluted with water can form a very porous surface that could lead to bubbles and variations in gloss, while some epoxy floor levellers can expand and contract at different rates to the tiled floor and lead to grout lines becoming visible once again (so-called “ghosting”).

Lastly, ghosting in the form described above tends to happen gradually, however grout lines can also show through immediately in some cases. The biggest offenders here are metallic flooring systems. Metallic pigments typically flow and settle freely in low-viscosity resins and consequently are excellent at finding any low spots. Even if you can’t feel the grout lines anymore you can still end up with a visible grid pattern, so you have to be very careful when applying these types of floors over tiles.

Grout lines showing through under a metallic floor applied over floor tiles.

Tile removal

Often the condition of a tiled floor will simply offer no alternative other than to remove what’s there and get back to clean, sound concrete. The actual lifting of the floor tiles is done relatively easily in most cases; it’s the glue underneath that can catch contractors out by being very stubborn and time consuming to remove/flatten. Another thing that can slip through the cracks with tile removal, so to speak, is the damage done to the concrete during this process. If you’re not planning to use a floor leveller, you’ll generally need to allow for a fair bit of patching to repair divots and chips before the resin floor goes down.

Overall, my opinion is that you should aim to get back to concrete whenever possible when it comes to resin floors. The path you take at the end of the day, however, will often come down to the preferences of the client and how they feel about the extra costs, time and risks associated with either option.

How do you approach floor tiles? Do you insist on removal or are you confident enough to go over the top?

Take care and talk to you later,


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Epoxy application - are you a painter or a flooring applicator?

Lots of people think floor coatings are just like standard house paint and ask their painters to do the flooring for them as well.

Is this a good idea? Do you really need a flooring applicator or can a painter do the job just as well?

Of course they appear to be very similar trades in that they both use brushes, rollers etc., but there are actually several key differences between them and I think you need to be very careful when choosing one over the other.

Painter v floor coating applicator

As a general summary, painters

  • Are used to applying low-viscosity paint, with up to 60% solvent or water content, in thin films and solid colours.
  • Use products with long working times.
  • Are used to applying onto walls and roofs with simple hardware (including low-pressure spray equipment).
  • Have a clear idea on preparation of metal, plasterboard and cement sheeting, but not so much concrete.
  • Tackle floors as well, but treat it like an extension of a painting project.

In contrast, flooring applicators

  • Are used to higher viscosity materials, i.e. high solids or solventless, applied in thicker films and often with colour blending techniques.
  • Use products with shorter working times and have skills to combat this.
  • Are more focused on preparation because flooring is their “bread and butter” and they understand these surfaces get abused.
  • Own their preparation equipment, e.g. diamond grinders, shot blasters.

Painters and floor coatings

With the observations above, you can see why painters might have a tough time getting the best results with a floor coating. Having worked with paints for so long, I’ve found the biggest hurdles they face with floor coatings are the shorter pot life, relative “stickiness” to apply, and expense per litre/gallon. Because of these three things they almost always have a desire to thin the product down with solvent, which in itself can lead to a host of issues an inexperienced floor coating user might not be aware of.

I know there will be people out there who don’t feel there is a big difference and will correctly argue that painters put down thousands of square metres of flooring. While that’s true, the question I have is how many of these floors stand the test of time? With the failures I’ve seen over the years, I feel the chances of incorrect product selection, solvent entrapment and delamination through poor preparation only increase when the client has asked their painter to do the flooring as a convenient add-on.

Painter v applicator suitability

It’s obviously important to choose the right trade for your flooring project and, in my opinion, I’d stick with floor coating applicators. Asking a painter to apply the floor, or an applicator to paint the house, simply isn’t the best use of the skills these trades have. This isn’t to say that one can't make the transition successfully to the other, but it takes time and only works if they’re committed to learning the right way. In fact, with the right training and the right habits under their belt there’s absolutely no reason why painters can't become great flooring applicators!

Finally, I certainly don’t mean to be critical of one trade or the other. They each have their own set of skills that are orientated around their bread and butter products. As a manufacturer of solventless two-pack floor coatings, the majority of users I work with are classified as applicators and I think it's important to understand that distinction.

Let me know if you agree with my thoughts.

Take care and talk to you later,


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Health and safety - what's the big deal about solvents?

Being a manufacturer of solventless epoxies means I get asked about solvents a lot, so I thought I’d go over my personal opinion one more time.

While my ties to two-pack, solventless epoxies have a lot to do with their performance, I was definitely drawn to them from a health and safety viewpoint as well. Right at the start of my coating career I got badly sensitised to MDIs used in polyurethanes, and from that moment I vowed to stay away from “nasties” as much as possible. Besides MDIs, the thing I most wanted to get rid of was solvent!

Solvent risks

There can be plenty of other bad stuff in coatings as we know, however solvents were front of the queue for me because I knew they didn’t have to be there – solventless epoxies were already being used successfully across all the coating fields. The stench was the most obvious turn-off initially, but since then I’ve found solvents have also been known to cause short-term effects such as –

  • Dermatitis and miscellaneous skin problems (drying, cracking, reddening or blistering).
  • Headaches.
  • Drowsiness.
  • Poor co-ordination.
  • Nausea.
  • Unconsciousness and even death (in extreme cases).

And have been linked to long-term impacts on –

  • The brain and nervous system (including memory loss, sleeping disorders and irritability).
  • The skin.
  • The liver.
  • Blood production.
  • The kidneys.
  • Fertility of both males and females.
  • Unborn children.

Solvent risks go beyond contractors

I come across plenty of contractors that blatantly scoff at those concerns – “I'm tough, she'll be right,” is a common attitude in our industry. Well, my response is the cemeteries are full of macho men, and you shouldn’t have to sacrifice your health for work. Others believe they're safe with organic vapour masks even though solvents are clearly more than just an inhalation issue. You can’t work in full-body suits, so what do you do? The answer for me is simple: get rid of solvents.

The logic behind going solventless, or at least minimising them where possible, only becomes clearer when you consider the people who live or work around coating projects. In my humble opinion, if you’re working indoors with a solvent-borne product then you’re downright negligent. One horrific story told to me by a father always springs to mind here: his son was helping him out on a job and mixing a solvent-borne coating in a 20-litre bucket when the vapour tracked through the building and was ignited by a cigarette smoker. The outcome was third degree burns and other life-changing injuries.

Solvent risks are not only during application or for seven days after either. Solvents can slowly be released for years (see the post on out-gassing here) and contribute to medical conditions such as Sick Building Syndrome. This illness has emerged on the back of modern building practices that aim to conserve energy by sealing up buildings as much as possible. As a result, natural ventilation suffers and, when combined with the release of chemicals in modern materials, creates a dangerously low indoor air quality.

I stumbled across an article published in The Australian Financial Review a few years ago that gave a glimpse into this problem. It claimed people spent 90% of their time indoors, in buildings that “are two to three times more concentrated [with pollutants] than outside.” Even though this was based on Australian data, I dare say many other developed countries would have similar statistics.

It also presented an example of “a woman who moved into a mass-produced project home built with materials that give off significant levels of formaldehyde (a VOC). After living in the house for 6 months, the woman went to a house-warming party in an identical but brand new home in the neighbourhood. On immediate contact with the powerful levels of formaldehyde in the new house, she collapsed. What happened was that her body had become over-sensitised to the chemical through exposure to it in her own home.”

The article concluded by quoting Green Building Council of Australia executive director Maria Atkinson, who says, “The full impact of poor indoor air quality has yet to be recognised...indoor air quality is the most serious environmental issue that has not been addressed in this country.” With solvents playing a starring role in these dramas, it seems the easy fix for everyone is to at least minimise the amount being used in the first place.

Poster of magazine cover promoting article on solvents and indoor air quality.

Going solventless

If solvents are so bad then why do people still use them? I think the main reason why contractors, in particular, resist change is because they're worried they won't get the hang of solventless epoxies. However, having successfully introduced many epoxy users to solventless technology over the years, I’ve found it’s only a matter of time before the confidence kicks in. Yes, the products feel a little sticky to begin with, but over time this perception disappears as they realise these products actually do behave. Importantly, many contractors are astounded at the immediate health benefits they notice. If they work with solventless epoxies for a week and switch back to solvent-borne they really notice the odour, sore eyes, raw throat, headaches and solvent “high”.

As with any product, there are techniques you should learn in order to make a transition as seamless as possible. Speak to the manufacturers about the best ways to apply the product and understand the capabilities/limitations. Have a play before you take on a job and be thoroughly prepared before you start. If you do all these things then you’ll find switching over to solventless epoxies can be quite painless after all.

Take care and talk to you later,


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Epoxy opinion - what makes an epoxy expert?

Time for a bit of light-hearted thinking on the topic of experts in this serious world of epoxies.

I guess there are a lot of definitions for an expert, but, in a real sense, who and what are they? Why do so many people try so hard to act like an expert? Why do they like boasting about having the same opinion as an expert? I've never really understood what all the fuss is about to tell you the truth.

Why do we think experts are so important?

The classic Oxford dictionary defines an expert as “highly practiced and skilful or well-informed in subject.” Well, there’s no doubt some people can legitimately claim to be that, however the coating industry is unfortunately littered with wannabes. Why? In my opinion, it seems people need to either satisfy their ego or justify their job title. Others pretend because they’d like to help, which is admirable in a way, but only end up making things worse.

On the other side of the coin, some people go to an expert just to get an opinion that supports their own; perhaps it makes them feel important if they're backed by someone with a title. You know, great minds think alike and all that. My tongue-in-cheek response is: “small minds rarely differ.”

I don't know about you, but I would only consult a so-called expert because I wanted to learn and for no other reason. I can humbly accept I don’t know everything and hence I look to be better informed wherever possible.

A different view of experts

A common perception of experts is that they know everything, but I just see them as people that know more about one particular topic than I do. An even better way of look at them is: “An expert is someone that has made all the mistakes in a very small field”. Either way, I would definitely exclude myself as an epoxy expert because I learn something new every day and continue to make mistakes regularly; and, I'm not ashamed to admit it!

I want to learn, seek information, question my beliefs and continue to look for better ways; I want to engage with people who have “made all the mistakes” in epoxy formulating, manufacturing, preparation, application, repair, maintenance and sales, so that I don’t have to.

Epoxy School isn’t about experts or egos

While I do not claim to be an epoxy expert and have no attachment to the term, I’ve come to know a lot about certain topics because of my desire to learn off these people and try things myself. Epoxy School is all about passing on this knowledge I have gathered as well as providing an environment where other epoxy users can ask questions and, more importantly, find answers. There are no “experts” here...or egos to stroke.

So, if you know more about a subject than I do then don't be shy, write a comment! I certainly won't take offence because I might just learn something. Better yet, why not put your hand up to contribute your expertise via written articles or videos?

Finally on the topic of experts, when someone wants to label my desire for learning and teaching as being some form of epoxy expert, I cheekily quote the following...it’s an oldie, but a goodie –

Expert (pronounced “X” - spurt): “X” being an unknown, “spurt” being a drip under pressure. Collectively, an unknown drip under pressure! Now, who would ever want to be an expert!? Haha.

Take care and talk to you later,


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Decorative epoxies - the polished concrete and warehouse looks

You’ve been asked to do a polished concrete or “warehouse” look for a client with your decorative epoxies – what do you need to know?

The traditional form of polished concrete involved 10-12 passes with a diamond grinder to hone the concrete into a smooth, glossy surface. While this type of flooring has been extremely popular in recent times, not every slab can be polished successfully and pricing is typically at the higher end. Because of this, a somewhat simpler and more cost-effective alternative can be done through the use of clear epoxies that rely on the resin to flatten the surface instead. This can be a very basic “grind and seal”, which results in the more rustic warehouse look, or, with the right product and thicker films, it can create a mirror-like, genuine polished concrete look.

Either way, if you think the idea of slapping a clear epoxy over concrete is a walk in the park, don’t be so sure! Believe it or not, there are few traps that regularly catch contractors out when taking on jobs like this.

Change your preparation goals

First and foremost, the polished concrete look and warehouse look will benefit from a slightly different approach to surface preparation. The natural inclination for many contractors is to whack a big, heavy grinder onto every slab and keep going until it’s completely flat. While there’s nothing wrong with that thinking as far as thorough preparation is concerned, ripping the tops of every high spot results in patchy, inconsistent aggregate exposure that rarely looks great in the final product. Instead, you want a grind that follows the contours of the slab and only removes the top layer across the entire area. An example of this type of thing is something called Diamabrush, which uses diamonds on flexible brushes to do just that.

Clear epoxies aren’t dead basic!

Ok, so you have a freshly prepared slab with a relatively even “salt and pepper” appearance. From here many contractors would simply mix up their clear epoxy, pour it onto the floor to roughly spread out, and then start back rolling. The problem with this practice is you can often see a dark patch form under the thicker sections of the poured clear epoxy – what I call the “pour line”. You can never fix such a blemish if it shows through the final coat, so you need to prevent it by changing your approach when working with clear epoxies, i.e. working from a roller tray is generally a safer option on the first coat.

This type of staining effect can also cause headaches in other situations, especially when applying in warmer weather. In these instances, the hotter conditions lead to large variations in the viscosity of the clear epoxy, i.e. freshly mixed product is thin and soaks into the slab easier (looks darker), whereas older product that has begun to gel is much thicker and doesn't penetrate as much (looks lighter). The result of this viscosity difference is the appearance of noticeable bands across the floor corresponding to the rolling pattern used, and is particularly visible where an old mix meets a new one. Once again, there’s no quick fix and prevention through measures such as smaller mix volumes is the only way around it.

Another potential trap when working with clear epoxies is the formation of “holidays” or, in simple terms, missed spots. Unlike the staining that happens on the first coat, holidays are more common in latter coats when the finish is darker and the clear epoxy isn’t as easy to see. Unfortunately these defects always have a habit of standing out much more the next day and can only be rectified with extra coats and extra cost. I’ve found the use of low-level lighting to be an effective way of reducing the number of misses, however there’s no substitute for working carefully and using a slow, methodical approach to application.

Your clear epoxy must be capable

The final point I want to make on the polished concrete look and warehouse look is an important one: you have to make sure your clear epoxy is actually capable of delivering the finish you’re after. The main focus in this sense is how well it flows/levels and the gloss it can achieve. The warehouse look is pretty forgiving and many clear epoxies will be suitable for that type of finish, however, I know from experience there are only a handful of clear epoxies that can make a good fist of a high-end polished concrete look. Regular readers of Epoxy School will know I always come back to doing homework on products before committing to any projects and it certainly isn’t any different here!

Take care and talk to you later,


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Surface preparation - does priming and sealing guarantee better results?

I know many contractors that prime or seal on every job, but does it always guarantee better results?

If you’ve read previous posts, you may recall I actually consider primers and sealers as different products based on the roles they perform (you can read the original priming and sealing post here). Regardless of what they’re called or how they’re used, a big question that comes into play on this topic is whether you always need to prime or seal. For me, the answer is no.

You can buy products that stick well directly to the substrate, eliminating the need for what I call a primer; you can also get well-laid slabs that aren’t porous or powdery and won’t need what I call a sealer to hold the surface together or prevent bubbles.

To take the argument against priming or sealing EVERY time a little further, I can even give you examples where it actually caused trouble rather than solved it. In one particular case I remember, the use of a sealer only managed to compromise the adhesion and cause some massive headaches for the contractor. There’s actually a lot to learn from this story and it’s worth covering in detail, so I’ll break it down for you here.

Flooring failure in garage caused by misuse of sealer.

Priming and sealing problem – beginning

The contractor at the heart of it all wanted to make sealing a standard step in all of his garage flake jobs so he could overcome the variation in concrete quality he was seeing and simplify the quoting process.

The solution he came up with was to apply a certain water-based epoxy (WBE) as a sealer on all the slabs. Being a very cheap product, the overall increase in material cost was minimal and far less than other sealing options – a big bonus in his view. The product manufacturer also recommended adding extra water to make it easier to apply and allow it to soak into the slab more. Fantastic! Even less cost.

Intercoat adhesion tests were conducted to prove the concept and the water-based epoxy failed concrete every time. It was fast enough and seemed to seal the surface well enough, so his plan all seemed to be falling in place.

Just when he thought he had it all worked out, a few problems began to appear. On one floor a small piece of coating let go directly beneath a rear wheel. Hot tyre pick-up, as it’s known (read more here), is a pretty common occurrence on garage floors covered with cheaper floor paint. The heat of the rubber softens these films, creating a temporary bond strong enough to prise small sections off the concrete. For two-pack epoxies, however, the heat isn’t an issue and this kind of failure can normally be traced back to surface preparation instead. When the underside of the failed coating was examined, there was a full layer of concrete visible suggesting that wasn’t the problem either. Something else was going on.

At the time it was determined to be particularly weak concrete at fault, probably due to it being rain affected or something like that. Anyway, the area was patched and life moved on.

More time passed and another failure popped up...same problem, different floor. Initially the same conclusion was reached, but maybe there was more to it? One failure wasn't enough to be concerned about and two in the space of a short time could’ve just been a coincidence, however some digging was done anyway to see if a pattern was emerging.

Priming and sealing problem - diagnosis

We understood the system worked fine on sound concrete via the adhesion tests, but when a weak slab was subject to stress (hot tyres in this case), the concrete would let go. We suspected the water-based epoxy was doing its job of sealing the slab to make it less porous, but was it somehow compromising the adhesion?

Further analysis revealed some very interesting facts. The WBE was a high solids product, but when diluted as per the instructions it would end up at 45%. Based on the coverage the contractor was getting – 1.35 litres/0.36 gallons of solids across 36m2/385ft2 floor – it meant a build of 37 microns/1.5 mils was being achieved at best, which isn’t much of a sealer at all!

In fact, very little resin was penetrating into the slab to provide the reinforcement these weak slabs needed. Because not enough was being used, it was simply sitting on the surface and forming a very flimsy basecoat of sorts that offered no extra cohesive strength to the concrete at all. Ok for good slabs, but disastrous for weak slabs.

The underside of the coating showing how the sealer didn't prevent the weak concrete from failing.

Priming and sealing problem - solution

The only solutions to this problem weren’t exactly what the contractor wanted to hear –

  • Apply the water-based epoxy thicker and boost the amount of resin per square metre to provide a proper seal for the weak slabs. The downside of this was the WBE became much less cost-effective and cured too slowly.
  • Use a solventless epoxy to seal the surface. Without adding any solvents, he could pull down the product to 150 microns/6 mils which would be sufficient to seal and prime the surface. The downside was this approach would add too much cost to each project and eat into the profit he was trying to make on each job.
  • Not apply a sealer and instead apply the basecoat at 30-35% thicker to allow for the absorption that would take place. Applying it thicker would leave enough product behind to flake into, but again it meant more product and more cost.

The moral of this story is you must ensure
primers or sealers are being used correctly and fulfilling their intended purpose or you could end up making the problem worse. Just putting a primer or sealer down in any old fashion definitely doesn’t guarantee better outcomes.

What is your experience with primers and sealers? Have you ever been in the situation where they were causing problems rather than solving them?

Take care and talk to you later,


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