Help With Gelcoat In Fish Mold

There could be a lot of factors in this
Moisture
Not enough catalyst
Age of gel coat
You might get it to set up by mixing a hot batch and going over the semi set one but it may not work depending on what’s going on between the fish and the gel coat.
I always seal them first with lacquer before I do a gel coat to seal in moisture.
You might have to scratch it off and start over if the fish is ok or try your luck on another one. Sometimes things get omitted when we write things down for publication

 

I'm no expert here but you are trying to make a cast from an already poured mold, right? Here's my experience with gel coat and it's somewhat limited in casting. If you do not get it mixed up properly it can take forever to set, it almost seems like gel coat without hardener with set quicker. Also not enough hardener, which this sounds more like your issue, will cause this. I'n one of my previous career, auto body, when using chop it got embedded in a wet coat of gel and then smoothed over with more gel. When it comes to strengthening a cast I would think you want the outer layer, detail layer to set up and then spread another tack layer of gel to that and then embed the chop into that.

 

I don’t use gel coat just bondo/resin. Gel coat costs to damn much these days!

 

Turkey, resin and cab o sil mixed is not gel coat! True gel coat contains titanium dioxide. The heat people talk about is not going to happen when your gel coat or resin is spread so thin. Only in bulk will heat be created. Your gel coat needs to be wax free and the MEKP that comes with resins is usually bad because it is photo chemically reactive and sold in clear tubes. Get some good MEKP like High Point 90 and keep it in the refrigerator. If you still have the fish coated, take it out and put it in the sun or under UV light. There is so much misleading information posted about fiberglass resins, like adding both hardener's to a bondo resin mix, and that resin and bondo is gel coat. NOT! Get some good quality MEKP, coat your part and set it in the sun. If you do not see a color change when adding your hardener, you have not added enough

 

Crab lover knows what he is talking about he does a lot of glass work. I would follow what he tells you for a superb product.

 

Yeah I’m not pretending it’s a gel coat. It’s bondo and fiber glass resin.

 

Cab o sil should not have a shelf life at all as it's made to absorb the resin unlike talc in bondo. Bondo's filler is talc to make sanding easier. Micro balloon's, Cab O Sil etc. absorbs the resin into a monolithic bond, creating a much stronger part over bondo. Fiberglass resin is also not waterproof but true gel coat is. Bondo and resin although not gel coat does work however it is far more brittle and not as strong as gel coat. Bondo and resin will not work for long term production molding and will chip and crack from undercuts and stressed areas of your mold. Bondo also has wax that rises to the surface as it cures. This wax can cause issues in the layup of cloth or strand layering. For a very strong production mold true gel coat should be used backed up by cloth or strand or a tooling gel coat. One of the biggest mistakes when molding and casting is using both gel coat and resin that contains wax. All your resin materials should be wax free and use a good quality MEKP like High Point 90.

 

Turkey, you are using the wrong filler for fiberglass resin. URE-FIL 9 is a thickening agent for rubber and silicon molding. Being silica based, it's shelf life is caused by moisture saturation from the air. You need to use a resin filler like Cab-o-sil or Micro Balloons instead. Get the proper filler, and a better MEKP. Keep your MEKP in the fridge, and when you add it to your resin and mix, you will see a color change in the resin. If you don't see that change, you need more hardener. You can speed up the setting time of your catalyzed resin by exposing it to UV light. Mix up a test batch of your catalyzed resin and brush it on two pieces of cardboard, then set one in the sun. Check back to both pieces in 15 minutes and see which one has fully catalyzed. Hope this helps!