I am planning to buy a gel coat spraying machine (external mix), I was wondering if I could use polyester resin with pigment and catalyst instead of gel coat, as I am trying to reduce my cost for the pressure laminated tanks that I am producing, would I have the same finish as gel coat? what is the main difference? I know that gel coat is made of resin, please help!
Make a test part. But I dont think it will look as good or have the same finish as you want to acheive. I have put a clear gel down then a pigmented resin behind it with a woven cloth… That is OK and gives a good gloss but never just pigmented resin and glass.
Depending on shape and finish on the mould you will likely find that the resin as a surface coat will likely separate,fish eye or run/pool on certain parts of the mould because it doesnt have the viscosity of Gelcoat. Normally adding additives like silica can help but its something i have played with before and i personally found that a gel coat will save you less hassle and less chance of issues occuring.
I hope this helps you…
You will not be able to achieve the cure you need out of using a pigmented resin as a gelcoat. Geltimes and cure characteristics are completely different. Resin generally has a longer geltime and generally longer cure phase to enable you to either laminate thin or thickish laminates. Gelcoats have geltimes ranging from 12-16 minutes and have a very reactive cure phase to cure the film your applying. The difference between good gelcoats and bad ones are how user friendly they are. Meaning if you compromise catalyst levels or film thicknesses it won’t wrinkle or alligator on you. Recommended film thickness are a minimum 20-22thou or .65mm wet. That way you have enough gelcoat at the correct catalyst level to achieve the desired cure of the film. Temps can also play a role as well so be conscious of these as well. UV resistance if your parts go out in the weather will also be a factor. You will gain some uv resistance with the addition of the pigment but not enough to outlast the parts life.
If resin and some pigment was just as good, the gelcoat manufacturers would have a hard time keeping themselves alive.
Some products can be made without a gelcoat, or just a pigmented resin. It is all about visual appearance, durability and properties.
When ever I paint the part post demold, I tint my resin.