Epoxy School Blog

Patching concrete floors - is a "bog" good enough?

You strive for the best flooring system possible, so why perform concrete repair with any old “bog”?

Perhaps “bog” is a slang term from my part of the world, but generally speaking it’s a cheap patching compound used to fill cracks and voids before over-coating. The timber industry has a bog, the auto industry has a bog, the building industry has a bog – but, in my opinion, the concrete flooring industry definitely should not have a bog! Let me explain why.

What is a bog?

A bog is typically a highly filled, fast-cure product with very little resin in the mix. This makes it cheap, but prone to inconsistent adhesion and that’s exactly what you don’t want in a flooring environment. So what type of patching compound should you use?

A resin-rich epoxy patching compound being applied into a divot.

Patching compound wish list

In my opinion, I want to do
concrete repair with a product that has the following properties –

  • Resin rich – a two-pack epoxy system that is rich in resin so I don’t have to worry about adhesion. When applying patching compounds, you find they tend to dry out as you scratch and scrape it across the concrete. If you start with a compound that’s dry to begin with, it will quickly become unworkable and the adhesion even more of a concern. 
  • Ready to mix – a pre-formulated, ready-to-use patching compound eliminates the inconsistencies adding in bits and pieces onsite can introduce.
  • Thickness range – a patching compound that be high build or feather edge and maintain its shape regardless. Being a high-build product, I wouldn’t want any solvent or water in it as you could end up with solvent entrapment.
  • Working time – a longer standard working time is appreciated because patching can be a slow process, with the option of fast or slow cure a nice bonus.
  • Can be sanded – while sanding afterwards isn’t the aim, I’d prefer to have something that can be sanded if required.
  • Compatible – the patching compound would be totally compatible with my basecoat, e.g. didn’t cause blushing, so I could apply it wet on wet rather than having to wait for the patch to harden or dry.
  • Tintable – although not critical, I would also prefer the patching compound to be tintable in case patching was required between coats and there was a chance it could show through.

Do you have a good reliable patching compound available to you? Perhaps you have had to build your own patching compound?

Take care and talk to you soon,


Read More »

Gloss or semi-gloss floor - which one to use?

When do I recommend a full-gloss over a semi-gloss floor  or vice versa?

Sounds like a simple question and many people will just tell you, “let the client decide.” There’s nothing wrong with this approach as long as you can educate them effectively on the differences between the two and why one may be more suitable than the other. Below are a few points you’ll need them to consider.

Full-gloss and semi-gloss floor in a restaurant.

What you expect with a full-gloss floor

Looking at the fundamentals, a full-gloss floor will –

  • Tend to be resin rich so it can flow to produce the smooth, gloss floor. Being resin rich also means that it might well be more expensive per litre than a semi-gloss floor.
  • More readily show defects in the floor, so getting the substrate flat and keeping the area closed off tightly are very important.
  • More readily show porous sections in the slab where the floor coating has been absorbed.
  • May be more prone to colour separation (read post on colour separation).

What you expect with a semi-gloss floor

Conversely, a semi-gloss floor will –

  • Often be cheaper per litre as it may have more filler.
  • Not show defects as readily. You’ll be able to see divots in the slab, so you should still aim to start with a flat and even substrate, however it will be less noticeable if dust or fluff has ended up in your floor coating.
  • Easier for the client to maintain as it might not show dirt and dust as easily and will tend to conceal scuffs and scratches better.

After reading that summary you’d be forgiven for only wanting to apply the more forgiving semi-gloss floor. That might be the case, but I still think you should always come back to the original answer: let the client decide.

Costs and defects can be explained

If your client is set on a full-gloss floor, you can now at least inform them why it might cost them a little more – the product might be more expensive, the preparation needs to be more thorough and you may need to seal the slab or apply an extra coat if the slab is porous – and why it’s seen as a higher risk in terms of bugs, dust or fluff. You should also advise them that day-to-day cleaning of their full-gloss floor will take a lot more work than a semi-gloss floor.

It also goes without saying that before you offer your client a full-gloss floor you should’ve tested the product and know you can deliver the result the client is wanting. If you haven’t or you’re not sure then you’re probably better off to not take on the job.

What other reasons have you come to learn for choosing a semi-gloss floor over a full-gloss floor?

Take care and talk to you later,


Read More »

Epoxy colour separation - pigmenting clear epoxy

Have you ever seen a colour difference when rolling out a floor?

Let’s use a common example to illustrate the problem: you’re aiming for a simple mid-grey floor and go down the path of adding a pigment pack into a low-viscosity, clear epoxy. You’ve already rolled out the first kit and it all looks good, however when you roll out the second you notice a clearly different shade of grey along the wet edge. Ouch! The client isn’t going to like that! 

Colour separation on a grey epoxy floor.

It’s not always the epoxy pigment’s fault

If you don’t understand why this type of defect happens then you’re probably going to blame the epoxy pigment batch. The pigment may well be a potential source, but what you’re seeing more than likely has something to do with physics instead. Let me explain.

Using the same example, we know that grey epoxy pigment is made up of mainly white pigment with a bit of black. In the epoxy industry, the majority of white pigments are based on titanium dioxide, which is a heavy pigment with a specific gravity of around 4 (compared to water at 1). There are different forms of black, but let’s say the black in this example is a carbon black, which has a specific gravity around 2.7. Anyway, if you put them both into a low-viscosity, clear epoxy then the heavier pigment will tend to settle at a different rate to the lighter pigment and, in a nutshell, that’s what causes colour separation in these instances.

What’s the answer to epoxy colour separation?

So, if we know that pigments settle at different rates, how do we control the problem? The key point to pick up on here is the epoxy pigments can only settle quickly if the resin is thin enough, i.e. it has no “body” to suspend the pigments. With that in mind, to avoid colour separation you’re far better off using a product that’s “tintable”, which means it’s designed to be used with pigments and will be specifically formulated to delay this settling from taking place.

I realise, of course, that sometimes you may not have a choice but to pigment a clear epoxy. If so, the best thing you can do is give it some body yourself by adding some filler. There are lots of different fillers to use and that’s a topic all on its own, however a kilogram or two of the right filler in an 8 litre kit will make a big difference (Note: if you’re splitting kits then adding filler will change the volume ratio). There are also other ways of adding body to a resin by using specialist thickeners, but we might go into that later.

Other epoxy colour separation issues

To finish off, here are some other things you should know about epoxy colour separation

  1. Some colours will show colour separation more than others. The biggest danger is when combining two or more pigments together, e.g. black and white in light grey.
  2. Some clear products will show colour separation more than others as well. Additives used in the formulation can have a big impact, good or bad.
  3. You also have to keep in mind that temperature will also affect the viscosity of the resin; in other words, colour separation may not have happened in winter, but that doesn’t mean you won’t see it in summer!

Have you ever experienced epoxy colour separation?

Take care and talk to you later,


Read More »

Epoxy non-slip flooring - five keys to success

Have you ever applied an epoxy non-slip floor that was too smooth/coarse in areas?

Over the years I have developed and specified countless types of non-slip flooring systems. Although there are many variations, I’ve found there are five keys to successful roller-applied, non-slip epoxy flooring (aka “spread and sprinkle” non-slip flooring).

The five keys for non-slip epoxy flooring

1) Flat substrate

With spread and sprinkle non-slip flooring, which relies on two films to sandwich a layer of non-slip particle/aggregate, you have to keep in mind the finished floor will reflect the surface profile. If you have a divot, there will be a low spot; if you have a crack, it might show through; the hills and valleys of an undulating floor will be visible. Getting the surface flat through levelling and/or patching will give you a much better result.

2) Film thickness

You might be able to stretch films out a little further on some jobs, but this is not one of them. Higher builds are generally required for non-slip epoxy flooring because there has to be enough resin to adhere to the substrate and bind all the particles together.

I’ve found a good figure to aim for is 60% particle coverage from the two coats, with the exposed tip providing the texture and wear surface. For quality industrial epoxy non-slip flooring, personally I wouldn’t put down less than 250-300 microns/10-12 mils for the basecoat, which works well with a 30 mesh particle.

The film thickness also has to be even. Too thick and you will end up with a smooth floor; too thin and the non-slip could be too aggressive or the particles too loose – to the point where they pop out. A consistent film gives consistent non-slip flooring.

3) Non-slip particle

A lot of contractors use quartz or sand, which has a Mohs hardness of 6-6.5 (diamond is a 10). That’s ok for light to medium traffic, but it’ll wear quickly with trolley or forklift traffic. For a harder aggregate, choose aluminium oxide or carborundum, which have a Mohs hardness of 9.

4) No substitution

The basecoat is chosen for a reason and substituting it can affect performance. Don’t get cheeky and swap it for a cheaper, thinner or stocked product.

5) Topcoat

My recommendation is to never use anything less than a fully saturated layer of aggregate in heavy-duty epoxy non-slip flooring applications. The most common argument for sprinkling a layer instead of fully saturating is to make it easier to clean for the client. While this is technically correct, if they're asking for such a thing then heavy-duty epoxy non-slip flooring is more than they need. Fully flooding the floor increases durability and helps produce a consistent profile.

Non-slip flooring – particle use

If sprinkling is deemed the best approach, the success of the floor will be determined by how evenly the aggregate is broadcast. There are many techniques for doing this, however I find grabbing a “knuckle full” (as opposed to a hand full) and lightly tossing into the air for the particles to settle randomly on the film is the best way.

As a rough guide to consumption, fully saturated floors based on 2 x 250-micron/2 x 10 mils coats typically use anywhere between 1-1.5kg per m2/0.2-0.3lb per ft2 of aggregate, while light sprinkling can be as little as 50-100g per m2/0.16-0.32oz per ft2. The thicker the films, the more aggregate you’ll need to add.

The right habits are everything!

It may sounds like a lot to remember, but it really isn't. It is just about developing the right habits from scratch. For those unfamiliar with non-slip epoxy flooring and looking for some step-by-step guidance, detailed instructions are available in the Eclasses.

So, how did my keys to success relate to the last non-slip job you completed?

Take care and talk to you soon,


Read More »

Garage flooring - flake flooring options

What could contractors possibly learn about flake floors? Aren't they all the same?

Some would say that flake flooring is fantastic; some would say it looks a little dated. In my opinion it’s a great type of seamless, resin floor for certain applications and garage flooring is definitely one (hence the title of this post).

So, what do I know about epoxy flake flooring that others might not?

All flakes aren’t the same

To start with, paint flakes can be made of different material and different processes using the same material (if that makes any sense!). For instance, I know I can buy flakes made of acrylic or PVA (vinyl), and there are different manufacturers of these flakes, hence there will be a great variety in the finished product available.

Overall, I have found acrylic flake quite brittle, which means I end up with a lot of “fines” in the bottom of each container. You have to be careful with how you broadcast these on flake floors as they tend to show inconsistencies really easily, especially when clumped. If you’re doing a partial flake job then I probably wouldn’t use any fines at all as they stand out even more and the client may look at it as a defect. 

Vinyl flakes are my preference

My preference is for the more flexible vinyl flake. The flexibility is beneficial not only with respect to fines, but it can also have another significant benefit with flake flooring. As it lands, a rigid flake will tend to create a lot of extra space in between and under the flakes themselves. These voids draw in resins, meaning you need more to adequately seal the surface; quite often another coat will be required to produce an even finish, which means more product and more cost.

Another advantage I like with vinyl flakes is I can get them to lie flat by spraying a mist of water over the surface. There are of course tricks and tips on how to do this (covered in the coaching Eclasses), but the result is flat, even, smooth flake floors that often don’t require sanding before being coated. Another cost and time saver!

Simple flake flooring = best flake flooring

There are obviously countless ways to do epoxy flake flooring and there are advantages and disadvantages with each method. For indoor applications, I like a simple two-coat process: a basecoat with full broadcast of flake and a topcoat. If you choose the right combination of flake and resin you can achieve a superb finish every time!

Question: I’ve always thought that “grey marble” (combination of grey/s, black and white) was the most popular combination for flake floors. A couple of years ago it seemed “coffee” combinations were the new trend  (combination of browns and off-white). What’s your favourite combination?

Take care and talk to you soon,


Read More »

Epoxy troubleshooting - epoxy "hail damage"

What is epoxy "hail damage" and how is it linked to so-called Benard cells?

The chances are you’ve already seen the effect of Benard cells but didn’t understand what it was or how to overcome it. The effect can take on a few forms, but one of the most common is the hail damage appearance, which can leave epoxy films with lots of little dimples or dents and looking like a car that’s just driven through a nasty storm.

Tiny cells cause epoxy dimples

 In very basic terms, Benard cells are the result of the resins behaving like other liquids when it comes to convection currents - a pattern of flow that sees liquids rising as they warm and sink as they cool. As the film hardens the flow eventually stops and you can end up with an epoxy dimple in the middle of these cells, i.e. hail damage. It’s definitely not good news if you’re expecting a flat, glossy film on a high-end decorative floor!

How can epoxy hail damage be stopped?

So, how can we prevent these epoxy dimples from ruining our projects?
Well, there are a few points to make about Benard cells and epoxy hail damage that will help -

  1. They tend to be more of a problem in clear, low-viscosity resins.
  2. They tend to be worse with higher builds. From my experience, anything over 400 microns significantly increases the risks of these defects. Before you start thinking, "I'll just apply all of my films at less than 400 microns", keep in mind that many systems need well over that thickness.
  3. They tend to be worse when applying on a heating cycle, i.e. during the late morning when the concrete is starting to warm. Ideally, you're working in the afternoon when the temperature is falling and the conditions aren't too hot (25C is perfect).
  4. Some products suffer less than others and you may be lucky to have a local manufacturer that understands how to minimise these defects.

Benard cells are always lurking

In closing, if you didn’t know about Benard cells and when they are most likely to occur, the chances are you’d simply blame the product for misbehaving. As I hinted at before, the Benard cell is actually responsible for several other common film defects, e.g. colour separation in pigmented films, so it’s definitely a subject worth getting on top of.

Have you ever seen epoxy hail damage? What other defects have you seen that you’d like an answer to?

Take care and talk to you soon,


Read More »



Latest news