A way to make lam resin thinner?

Hello, I find my resin a bit too thick, which is causing problems along the way. Especially when saturating the laps, my sqeegee really sticks to it, pulling out long threats. While hotcoating the resin hardly spreads.

Is there a way to make the resin thinner with some sort of chemical substance so it will soak and spread better??? Thanks!

Heat. Sounds cold to me.

Polyester resin may be thinned with styrene.

Epoxy resins may be thinned with small amounts (just a few percent) of denatured alcohol, although pre-heating works better.

Could be a temperature issue as well… if the resin is nice and warm it’ll flow much easier. My first winter glassing away from San Diego gave me nightmares!

 Howzit mook, Doc has one good fix but using styrene can weaken the lamination a little. I would first try heating the resin by putting the can in a bucket of hot water and see if that thins it out.Aloha,Kokua

some good advice here. With epoxy always try heat first, things like alcohol used to dilute epoxy don’t react so they can really weakend the resin and throw the mixing ratios all off. The good thing about most epoxies is that they don’t have alot of volatiles, so they don’t thicken up by evaporation like polyester does.

Styrene in polyester, on the other hand, does crosslink into the resin, but you still don’t want to add more than 10-20% at most and really only when you know your resin has thicken because of evaporation and not temperature. As a last resort, adding styrene can revive some old polyester than has lost fluidity due to evaporation.

Hey Mook,

depending upon just how cold the room is, you would want to try heat first. Either heat the room (if below about 65 deg F) or heat the resin directly. We actually have a small microwave dedicated for this purpose. Since polyester is a hydrocarbon and microwaves effectively excite carbon molecules in order to create heat, be careful not to overheat. I recommend about 8 or 10 seconds then catalyze and lay up. If the room is too cold, then the resin will cool as you work and begin to thicken, if this is the case then a heating of the room will be necessary.

Styrene is a good second choice as long as not too much styrene is used. This will be especially true if the resin is older and the styrene has evaporated out of the solution. Styrene breaks the chemical chains (mers) that make polyester resin strong and resilient. Too much styrene in the cured product will be brittle, so use styrene monomer judiciously. Styrene is also highly poisonious so do not breath the vapors or allow skin contact. Note that styrene is also the main ingredient in Surfacing agent so again be careful.

Hey nice one,

I really thought there was no such thing as making it thinner. I’m really glad I posted this question. Thanks you all!

The polyester I have probably got thicker because off evaporation. I use it in room temperature but I have it for over a year now and it got here in a plastic container which I know is making the polyester evaporate. So a while ago I poured it in a big tin can, which is better.

Silmar 249 straight from the factory contains 35% styrene, so a year or so in a plastic container it has definitely lost some styrene to evaporation. Start by adding 10% styrene, mix well as the styrene will be hard to mix in at first and keep adding until the viscosity looks right again at room temperature. As mentioned earlier, too much styrene will make it go brittle, so add just enough the get it usable.

Now i know you guys are going to shoot this down, but it has worked for me in a pinch or two. I use Acetone from time to time to cut the resin, not very much just a small cap full or so. Works like a champ, and I haven’t seen any brittle glass or what not. Yeah i know…chemical bond this, chemical bond that. Put a small cap full in your hot coat, and you’ll be amazed how smooth and perfect it lays down. Some time Stryene isn’t the most handy chemical to find.


Hi Mook

Living in the UK resin is nearly always a tad cold, Cleanlines on this forum once told me he used to use an old electric blanket when the resin was cold…work’s a treat. Failing that, a touch of Styrene also works well. Not to much though!