Hello. If one uses a infusion epoxy that is light amber into a black carbon fiber, will it make the black carbon fiber color appear off??
Negative. At least barely noticable to the human eye. My resin I use for infusion is dark Amber and it has zero affect on the color. I’ll post a picture of one of our parts tonight.
Simple answer no. But there is always an exception to every rule so I’m sure in some cases it’s noticble and the only real way to tell is experiment experiment experiment. One epoxy I use is Epoxy-N-Fusion from PTM & W and it is light amber, you can’t tell in the parts at all.
Try to stay away from clear resins. They always seem to be way more britle than tinted resins.
Thanks
Man, you really hit the nail on the head, cause that is the company I am going to be buying resin from. Great to hear your answer.
Thanks
Here is a picture of one of our parts. The resin we use has a very dark amber tint to it like I said. No problems though. 
The only time when you see it, is when you have bridging and a resin puddle.
If you are worried, add some black pigment to the resin, to make it just light-transparent grey-ish. This at least takes care of yellowing and yellow resin puddles. (it makes grey resin puddles…)
I do not share the opinion on clear resins being brittle. Some of the more tough resins I have are ultra clear.
Same here. One of my clearest resins is used to make wind blades 175+ ft. long.
… Well I’m dumb ::(:
I retract my comment :).
Big user of PTM&W as well, 2712 infusion resin as our standard “go to” resin. Good company, good product…they have a nice line of casting resins as well.
Many “clear” resins we use here end up amber or blackish after cure, and then most definitely post-cure. Cynate Ester for one is lightly tinted after cure, but once you post cure, even under vacuum, turns amber. You can see the fabric fine, but you also know which panels are post-cured or not, just by looking at it. However, it’s still black. Only if you NOTICE that the tint is amber, it will stand out.
VER esters with higher amounts of cobalt will also turn green. However, hardly noticeable at ALL on carbon. Only in glass will you see the color change of the various resins and mix ratios.
Most resins are clear, but the hardener have several colours. Sometimes red, yellow/amber, blue or clear.
My infusion epoxy ist absolut clear like glass. Prepreg resins a
have a amber colour after curing.
The red colour in the hardener comes most time from the amine groups, these are the hardener that does not smell fine.
Most hot temerature hardener have a amber colour.
The blue colour in the hardener should help that the parts will not become yellow throug UV light.
Sometimes a light black coloured resin can be useful in infusion of carbon fibre parts.
This is not alway valid just a reference point.
Blue coloured hardeners are also a safety measure, to assure you mix in hardener before infusing the resin… (I have seen a 64ft carbon boat being infused partly with resin only, no hardener…)
I have seen an infused wind blade mould only with resin and a lot of unhappy people. Thats a lot of garbage. Til that moment I thought that something like that will never happen, too mich or less hardener ok, but no hardener!
In my opinion the color of the resin isn’t nearly as important as what the color of the resin will become after some exposure to UV light. Many resins will really yellow/brown out after exposed to the Sun. Naked carbon parts then take on a nice army green tint.
Thats why you need to clear coat the parts with a nice high quality urethane clear :). ^^^
Lol before I got into composites I was an autobody tech at a few shops. Once I spread bondo on an entire quarter panel of an Ford E150 to then find out I forgot to add hardener :o.
In my deffence we used cream hardener so I couldnt tell…
With resins that have UV inhibitors in them a clear coat is unnecessary. Resin Research 2070, Adtech 820, and MGS 285 are some epoxy resins that infuse nicely and won’t yellow in the sun.
I assume that you are shooting the mold with your clear coat so you don’t have to shoot is after molding. 
The UV inhibitors in epoxys just slow down the yellowing process. The best UV protection is a UV clear coat or the polyurethan in mould coatin I use.
DDCompound, what kind of in mold polyurethane coating do you use? This painting after demolding is a lot of prep work.