Tooling gelcoat

I pulled the plug from the mold today. The mold looks really good. A couple of small spots I have to fix. A scratch and a small amount of alligatoring in one corner. Not bad for a first time effort.

rich

 

alligators happen !! as long as you understand the causes for next time !!

Ok
WHAT CAUSES alligators??

Usually its thin gel coat !! if there's insufficient thickness then the gel coat never cures properly !!

Next is uncured gel coat so this is related to the first one of thin gel coat .

Styrene attack is another one ,again all theses things related and linked to the first 2 but could also be caused by a slow second coat of gel coat or slow resin ! always use a slightly faster brew when going over gel coat with glass on your first skin !! .
If you used 1.5% the first coat the up it to 2.0% for the second coat !! I have found over the years that of I mix a small percentage of lamination resin with the second coat its much easier to apply and end up with a smoother surface to laminate over !!
The styrene in the gel coat or the resin is etching into and softening the gel below so this action is activating the sticky layer that should always be on the surface of the gel coat so the next coat will etch and bond 100% !!
A little trick is to tint a second coat of gel a slightly different colour so you can see it better and don't miss any where ! also brush in a completely different direction say 90 degrees to the first coat if its possible .
its also a good way if you have to sand the mould for any reason later you know when you sand to the different colour the glass will be very close behind !!

Is all this making any sense ??

 

If you're using polyester resin, especially when making a mold, you don't want to put a hot skin over the tooling gelcoat as polyester tends to shrink and that can cause pre-release and resultant deformities in the mold. You don't want to do it for molding production pieces either, for the same reason.

If you have alligatoring after a week or so of gelcoat cure, it's probably a good thing that you took a week to get around to laminating on the mold, as you might have had larger problems if you had laminated sooner. Brushing and rolling gelcoat never worked for me.

 

When I first started in glass work all gel coating was done by brushing !! was all we ever did !!,the company never had even a spray gun for painting ,contractors did all and any painting . brushing is a art and its amazing how gooder job can actually be made with the right kind of brush !!. Long soft haired brush's were a blessing and were treasured and locked away after being cleaned washed and dried . and if you had a gel up you were banished to the back blocks of hell till you learned your lesson and never did it again!!
Like I have said many times over and over, know the products your using !! become familiar and know and understand there properties and how to use and what there physical capabilities are and all those problems you used to have will all go away !!

 

I filled the imperfections, (mostly alligator marks, there were more than I thought initially) in the tooling gelcoat inside the mold with automotive spot putty. when its set up I'll sand them smooth. OK, then what's next? Can I touch up these now sanded marks with a small brush and tooling gelcoat and then sand them smooth? Or do I have to refinish the inside of the mold with Durateck or something else. I want to get it right, don't want a part to stick in the mold of course.

rich