Hi Joe, 

i have dyed epoxy and don't see any issue with it unless the dye is not compatible with or otherwise adversely changes the mechanical properties of the epoxy. so check with the manufacturer of both the dye maker and the epoxy manufacturer to see what you can glean from them.

so onto dying, i have not done it often, but have done it.  the main reason is don't do it often was mostly for the though process described below:

in in a question like this, typically the most important question is what visual effect am i trying to acheive?   and related to that, is the best way to acheive acheive the effect to do it within the epoxy vs changing the optics of the underlying material (e.g., staining the wood) or getting the effect in the outermost layer (e.g., paint or other finish). related to this, dyeing the epoxy will not typically address the need for a UV protecting layer of varnish or paint or clearcoat..so there will always be an outer layer.   and so i have just found that i have not often found myself (after puzzling it all through) wanting to dye the epoxy.

that said, we have a lot of super-creative people who build kayaks and they try all kinds of things.   doing a little test section on a scrap piece of wood is an idea i would put forth as a great way to try your idea before fully committing it to your boat.

h

   Thank you for your advice. This is certainly going to take me a while so I'll give it a go on some scrap. I'm not sure what the wife is hoping to achieve since I've got zero experience with any of this. She mentioned wanting to "catch a hint of color when the light hits it" but I think we've compromised on just dying the epoxy on the Hatch covers. We'll see what happens.

As Hspira points out, adding dye to the epoxy will give the boat some color but it will also hide the beauty of the wood grain some what.  From my perspective, the only real use for dye in epoxy on a wooden boat is under paint, where the dye can help hide any scratches that penetrate the paint (ie, black epoxy under black paint).

IMHO, stain is a much better approach with wood because it adds color while highlighting the wood grain.  If you go the stain route, you have to do it prior to epoxy touching the boat.  How to use stain is detailed here: https://www.clcboats.com/shoptips/finishing-tips/staining-your-kayak.html

If you go the stain route, I strongly suggest that you do some test samples before staining any of your parts.  Originally, I wanted to use Behlin Yellow on the hull of our Shearwater Double, but when I did a test my wife said that it looked like a dog peed on the wood.

Pictures below are Behlin Red on the Petrel Play and Cherry on the lower hull of the SWD.  I believe that Behlin has been rebranded to Mohawk.

I'm very interested. I would like to use a brown dye, because I'm not happy with the wood stuff for making big fillets. Using epoxy  thickened with silica/micro thingies and a dye makes a much smoother fillet in my opinion (and I have not to put my finger dipped in alcohol to smoothen them out). Anyone done this?

>> If you go the stain route, I strongly suggest that you do some test samples before staining any of your parts. <<

Yes to test samples. I wrote on the top of my build notes, in big block letters:

"DON'T DO ANYTHING FOR THE FIRST TIME EVER ON THE BOAT"  

to go back to rolfie61's question, it is when i am making fillets is when i have dyed the epoxy in my builds.

to put it in context, i often stain my boats dark, so when i have a fillet that is visible, i want it to match the color of the stain....but you can't really stain a fillet, which means you have to 'dye' the epoxy so that the resulting mixture gives the desired color.

so my approach to dying has been to take stain and mix it with half cups of wood flour and then let that dry out.  so i routinely keep black and various browns on hand.

when i make a fillet, once i get the fillet relatively close to mixed to the consisteny i want, i then add of my colored powder until i get a mixture of the final color i want.   so in this approach, i am basically dyeing to match a stain that i applied.

h

 Okay, h, so a lot of testing, trial and error. I have some spare wood to make samples. Thanks.

Rolf