spraying gelcoat

Thank you very good info

 

I would recommend to thin your gelcoat 10 to 15%
They will tell you to only use styrene but in my experience this will cause white gelcoat to yellow with age.

I prefer to use MEK as a thinner and have found Acetone to be a source of porosity probably due to its fast evaporation rate.

A 2.5 to 3.0 tip on an HVLP gun will spray gelcoat quite well with a minimal amount of orange peel at around 40 psi

For what you are doing the spraying should all be in one go or 2 back to back (Not over the course of 3 days), You may need to stop and clean your gun. Remember you only have about 20 to 25 minutes before the material will gel.

Spray a cover pass like what you would do with a wet coat of auto paint, wait a couple minutes to gas off and do the same, wait a few minutes and do the same with 5% surface agent mixed into the final cup.Or skip the wax and mist coat the fresh gelcoat with PVA 45 minutes later or once tacky.

Always catalyze your gelcoat at 2% mekp 10cc per 16oz or 22 drops from an eye dropper per ounce, if you are doing a very small quantity

Gun speed and distance you will have to experiment with, personally I hold the gun about 8 inches away.

I do gelcoat repairs frequently and never have problems with porosity or any other issues for that matter

 

Great info, thank you so much. Maybe a test panel first?
Like auto painting, water contamination in gelcoat would not be good, would you agree? I will make sure I will clean the surface to be with acetone?
I feel very fortunate that someone like yourself to chime in. Thank you again.. Gary

 

Thank you all for replying and your info! Gary

 

Any solvents added reduce the physical properties of the gel coat, the more you add the greater the affect. 15% is a lot.

Products like Patchaid are designed for this purpose and work well, they are made from the same base resins as gel coat, so it retains as much of the original properties as possible. They also contain addition promoters to help with the cure in thin films.