Use of colours with epoxy

Hi,

I'm just starting a new trimaran project and started making the first test outrigger from 3 / 4 / 6 mm marine ply in sticthc and glue.

I'm about to put on the outer layer of fireglass and wondered if anyone has any experience of colouring the epoxy?

I am thinking of either a blue or black final colour nad have seen that colours can be added to the epoxy - the thought being that if the epoxy is pre-coloured and scratches etc will barely show once it has dinged and clanged around aon various rocks/sticks/beaches etc.

Anybody any experience or thoughts on this? I've got some testers and am going to try on the inside first to see what it comes out like.

 

Welcome to the forum.

Epoxy can have pigments added, though epoxy will always need a topcoat (paint, varnish, etc.) of some sort to offer UV protection. Some epoxies have UV inhibitors in them, but these will break down (from UV) in time and damage the underlying epoxy and surface below. This said, you can use pigmented epoxy and a clear coat over it. You'll need to treat this much like a varnished surface, but it certainly can be done. If the goal is to use epoxy like gelcoat or a a finish coat, then pigments alone will not work. If you insist on this approuch, use graphite or carbon black as a heavy filler mix, along with some pigment. This will hold up the best, though (again) it will still break down from UV, without a protective overcoat of some kind.

 

I have used white epoxy pigment on a couple of rudder blades-they went cream in a few weeks.The same sort of colour as Bloodaxe foils,which may not be coincidence.

 

painting

Hi,

I didn't make clear I will be painting it - the coloured epoxy is jsut to sto pany of the paint scratches quite so obviously.

I'm going to put some on a hidden interior panel in the first outrigger to see how it works nad will report back.

 

What design are you building?

 

In this case, sure add pigment. Add the pigment to the resin first, mix well, then add the hardener.

 

I added pigment to the last layer I put on the hull. Not so much for scratch hiding but to help out in the fairing process. I am working in a poor light situation and the higher contrast helped.



You can see here it helped highlight the low spots.



It might work as you expect, I don't know.

 

This advice is good for fiberglass resin, not epoxy. Two part epoxies have to be well mixed first to start the chemical process correctly at the right proportion. It needs to develop its heat. You can then add colors or fillers as needed to achieve desired results. One minute for each stage of mixing.

I have used all knds of filler including sand, aluminum, zinc, wood. And the amount of filler will vary with usage and will change the hardness or flexibility of epoxy. But the ratio of the epoxy is always 50/50 or 5 to 1, what ever it might be.

As far as color unless I am doing a clear coat on a floor or wood table etc., I always add different colors. Black, red, gray, etc... these are used for sanding layers or to make sure that I have a true complete coat. A typical application will have 3 or 4 coats, usually all different colors.

On UV, not matter how good your epoxy is, or its UV proterctions added, it will always break down over time. Paint it and it might live forever. Also becareful not all epoxies are truly marine, some will let water through to the layers. Do not mix different brands or types. Add your layers withing 24 hours if possible.

Oh for colors I like powders, I use the color talc that they sell at Home Depot for string markers.The red and black go a long way.

 

Just doing a lash up adding outriggers to my dinghy initially which I am struggling to get around on as it is a quite tippy ISO.

Will then replace main hull once the outriggers and so on are tested and working well.

Just want to make it easier and safer to sail when I am struggling and give me insight into how things perform.

The first test outrigger hull needs the last touches inside and then I can get the fibreglass on the outside ready to test mount it.

When this is osrted and I have made up the trampoline I will be able to use it as a kind of proa at least with the added stability and get an idea of how it performs while I make up the other one.

 

My recommendation comes from one of the major formulators and is the way I've done it for years. I too questioned it initially, but now understand why your concerns aren't applicable. When resin is mixed with hardener, it reacts with the epoxy molecules, not the added pigment, so the reaction isn't diluted or otherwise altered. The pigment remains in suspension and doesn't interact with the reaction. I was told to mix the colorant into the resin first, just to make mixing easier.

 

PAR, I have been using epoxies and polyester for 35 years and learned a few things along the way and studied a bit of chemistry too. I had a company that built Aluminum Boats and Faired them with epoxies that we mixed. We mixed it by the trowel bucket, not an easy thing to do in 90-degree weather. I mention all this because there is a lot of misinformation along the away.

First, get away from the concept of resin and hardener when it comes to epoxies. They are two part chemical reactors. They require a proper mixing amount according to their ratio, if it is 50/50 then it is 50/50. Each Epoxy system has it own mix and tolerances that are possible. In other words, some epoxies allowed for a bigger mistake in mixing. Others have very little margin. But altering it from proper ratio will always make it weaker. And you don't make it harder by adding more hardener or make it cure quicker.

Mixing it properly requires every single molecule of Part A mixing with Part B, in other words, they have to touch. Then they combine and produce an exothermic reaction, they get hot. They have to stay together for a short period of time, to get to know each other, and fall in love with each other. This is called pot time. This is sometimes about 3 to 5 minutes.

Then when you add color, or filler whether a liquid or powdered these become suspended in the mixed epoxy which is no longer two parts chemically. The total mix then continues to harden, with all its strength and indeed the particles in suspension may alter the physical properties of the material but not its chemical properties.

If you add the color to Part A then when you mix Part B not every particle will fall in love with the other. There will be a loss in strength, which may not be noticeable depending on application. It may work, it may work for years, but it is still technically incorrect.

The other problem with mixing epoxies is the time factor. If you mix it properly and give it the pot time then the clock is running. The only reason that the advice was given to premix color to resin comes from Gelcoat, were if you have a whole boat to do and want a consistent color you pre-mix the whole resin can with a specific color and then add hardener as needed.

In epoxies we would put Part B which was typically lighter in cooler to extend working time, remembering the heat outside and that mixing itself generated heat.

Epoxy is all about mixing it well, and temperature control.

There is a lot of confusion between Epoxies and Polyester products. Polyester use the hardener to make the resin cook via a chemical reaction, but does not really need it as part of its formulation per se.

Hope this helps everyone cook with epoxy.

 

I too have been using epoxies for a long time (early 80's) and I also know it's chemisty, much better than you might realize. I know what the hardener is (an activator), though most wouldn't understand if you call it this, which is why the formulators also label them as a hardener too.

I too had the same concerns, until I looked at what most pigments (including the ones that tend to plasticize the cured matrix) are. The products I use don't combine, coat, mix or react with either the resin or hardener, though mixing with just the resin first does make it easier. I have no confusion about the various resin systems.

The real thing to worry about with pigments is what you're using and how much you do use. A lot of different things can be used, particulates, dies, combinations and different formulations. For example the stuff West System sells is a bisphenol base, so you better use less than 5% or you can screw the pooch on mix ratio. Others can screw with the hardness. The ones I use are pure particulates, which remain in suspension, regardless of mixing time or aggressiveness. If well mixed, all the molecules get to react with each other.

 

I mix the pigment into the resin first. Two reasons: 1) working time, once I start mixing the hardener side in I want all the time I can get for pot life, don't want to waste the pot time in mixing pigment in. Reason 2): The pigment I use is made with the same epoxy resin base as the epoxy resin I use, so when I mix it with just the resin side I can keep the final resin/hardener ratio constant. It may be true that in some minute way the pigmentsame in the resin may "get in the way" of some molecular bonds, but I would bet it's well within the margin of error in visual measuring and manual mixing. When I add pigment, it's almost always to a flow coat, not to a fiberglass lamination

 

Hi Joel, good to see your post. I saw some tests years back, with normal pigment mix ratios and the cured matrix did experence some lose, but it was less than 5% which is fine for a coating. I too wouldn't do this within a laminate.