finish on mould

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#1

hey all,

we’ve got a really nice mould of a bonnet (hood to you US people) and the surface is now really nice after quite a bit og 1500grit paper and g3 and g10 rubbing compounds. but as we are running out of gelcoat to sand down we have got a load of tiny little pin holes on the surface.

what can we do about it?
we dont want to sand off too much with the g3/g10 and end up going right through the gelcoat into the glass. this would ruin the mould.
can we just get it as good as we have and make a part from it and take the details off the parts?

how do you guys get a mirror finnish on your moulds or deal with tiny little pin holes?
we only put 3 layers of thin gelcoat on the plug when we made the mould so there is only about 1.5-2mm of gel to play with and we dont want to go through it.

is it worth trying to make a part from ti and see how it goes? or is it just scrap glass now?

cheers

L.

#2

why not just try and make a suare foot part on a part of the mold and see if the imperfections will sand out of the part pulled?

#3

sounds like pourosity it will sand out of part very easily but why did you get pourosity ----water in air line thin with wrong chemical? bad thing about pourosity is the wax builds up alot faster and parts start pulling hard

#4

well it was a wet layed mould with no vac bags etc. and we didnt thin the gel out at all. just brushed it straight on.

i was wondering if heat could have done this?
we used a body panel polishing powertool to bring the finish up on the mould. i found out later on today that when the polishing head was left in one place for more than a second or two the surface became quite warm quite fast.
could heat have done this?

L.

#5

That’s one reason I teach my class while making molds to use a different (older or ugly cheaper resin that no one wanted) color gel coating last so when you have to sand and it changes color, it is time to stop before you get into the reinforcements.

You might try using Duratec top coat to recoat the whole mold. I was going to try it over the summer on a repaired mold but haven’t got around to it yet.

#6

yeh i was wondering if in future i should use pigment or something in the gelcoat of the mould. its very hard to tell if i’m about to go to far.
so far so good but i dont want to push my luck :shock:

L.