So I had to repair some damage on a few molds and I was wondering what would work better. Spraying the molds with red tooling gel coat or polyester primer by Duratec?
I need it to be thin enough to level out well and not change the details of the mold. Body lines, grooves, etc. I’d accomplish this by adding duratec high gloss additive 1:1 or 2:1. The duratec being the, “1” in 2:1.
Thanks in advanced to anybody who can help me decide :).
John
Depending on the tolerances engineered in your mold, you’ll need to decide on what is most important.
1)- Too tight of tolerance to ADD material by spraying ?-(Make new mold).
2)-Slight openness to tolerance as long as thin application.-(Re-surface).
If you do pick #2…then sanding the mold surface will be the start and be sure to only rough the surface enough to get a mechanical bond-( read-lowest grit to avoid scratches showing through).
Once you’ve thinned and sprayed your Duratech…you’ll want to perfect the finish once again by fine ‘flat-stick’ and block sanding so you can polish.
Since you don’t want to have to remove a lot of newly sprayed coating…it is ultra important to lay that spray as slick and perfect-( read-without texture)…as humanly possible.
Otherwise you may lose detail or alter the final part too much. This is one of those times we wished we had made an additional Parent part/plug so making another even better ,perhaps, mold could be more easily done.
I’ve always been able to use the original plug/parting board to make a new mold faster than i can resurface an old mold.
Good point…certainly size can be a deciding factor in the case of mold size and material consumption . The smaller the mold…the more likely one is to re-build.
Size or time constraints. Something is going to win over…but if the repair didn’t work well…all time is lost.
Mould Coat is a professional mould recoating system. Anyone had any luck with this? It seems to be not cheap at all, but can save the life of a mould.
I usually would always just make a new mold but in the two molds I had were perfectly fine accept for a crack in each one where it went through the gel coat into the fiberglass reinforcement. From there on it spidercracked to the back.
I already grinded, applied VE tooling putty, some bondo in some areas, then built it a very nice wooden frame, fiberglassed, epoxied, and bondoed it to the mold to fuse it all together, and then sanded the entire surface down heavily with 36 grit paper and a DA. The reason I did this is because it was primed months ago after I wanted a nicer finish. This was before I started perfecting the plugs.
I’m ready to spray them but I still need to know what would work better. Tooling resin with duratec high gloss additive or duratec’s primer with the high gloss additive. The tooling resin is much harder I believe so I’m leaning towards that. I just want to make sure I do it right the first time.
I’ll post pictures tomorrow :).
Thanks for the great help! 
John,
I’m sure you’re going to do this, but in case you’ve missed it, tape out all the areas that you’re not resurfacing with Duratec.
Another thing I have experienced is that you don’t need a super high end gun to spray duratec materials. I’ve tried several and thought that this would help you. Although Hawkeye suggests not to use HVLP guns, in my experience, the best of course was to use the SATA 1000 RP. The next best and with extremely low orange peel was the 3M Accuspray the orange peel on VE high gloss top coat went away with 400 grit with the Accuspray. Even with the Sata I needed to start off sanding with 400 grit, 800, and then 1200 and compounding + polishing. The accuspray part number is 16570 and it comes with 3 1.8mm plastic disposable nozzles and the fan from them is fantastic. I diluted the VE topcoat with 5% MEK and catalyzed it with 2% MEKP. Use the accuspray at their max recommended pressure and fully open fan. Reduce the fluid volume to what you really need for one light coat. The accuspray I had the part distance of 30cm (12 inches) and 75% spray over lap.
All the best.
N
Thanks nash! I purchased a smaller tip for the gel coat gun we have and I’ll be using that. I’m very skilled with the dump gun so I"ll do very well with this. I think I’ll just be spraying red tooling gel coat with the high gloss additive. I’ll post pictures of the before and after :).
John