Why are we advised to use a non silicone based mould release agent?
I’m guessing it is because of it getting into the newly made component surface and prevents futher coats of paint or laquer perhaps? Does it not wipe off like the wax we use?
Just wondered…
We used silicone spray to “help release” a part from the mold… hahahha it didn’t work AT all. mold wax or semi-perms are the only way to go.
So basically we don’t use it because it er, just doesn’t work…
Thanks!
I hoped someone else would have commented on this before me.
I think the silicone reacts with resins. I know RTV tin/platnum catalyzed silicone systems release alcohol unless cured correctly, which can react with many resins, even plastics.
I also think the sprays and other stuff have other VOC’s that degas after use, which will contaminate the composite.
Somebody once told me TR 104 High Temp wax contains silicone.Thay said that’s what gives it the high temp resistance. That would explain why resin and PVA fisheyes on it as opposed to Partall which doesn’t?
Resin fisheyes on TR104 mold wax?:eek:
How are you supposed to gel coat onto/into the mold if using TR?
I’ve been using this:
http://www.specialtyproductsco.com/Honey%20Wax.htm
And always get fish-eyes when applying PVA release over the top of it, surely it is certain to do this anyhow? I learned from an early age (aged 6) that water based products don’t mix with wax (just like oil and water). We used to write or draw with a clear wax candle and then paint over it to highlight what we had written (the paint sticks to the paper around the writing and not to the wax).
Resin does the same also because it is so thin, only gelcoats don’t because of their much lesser viscosity - the wax cannot physically part it.
In my opinion you should either use PVA or wax, not both, although the only time I would use them together is on the first one or two pulls from a new mould, I find that wax is just not enough on its own here.
What I can’t understand is why you guys use ‘Semi-perms’ What are the advantages of this stuff?
This styrene vapour suppressant stuff looks good: http://www.specialtyproductsco.com/Styrid.htm
PVA Mist the first several coats on and not use wet passes.
Semi perm. is the cats meow. Once properly prep. the mold, you don’t need to re treat it more 6 months to a year later…or longer…
Yeah I can see how dusting the PVA on will help, but I found it left a very poor surface because the droplets just sat and dried rather than flowing out and going smooth. I’m guessing once you have done the first few light coats then you can lay it on heavier to get a gloss? I’ll give it a go, it seems a lot of time and trouble though.
So semi-perm is more perm than semi? 
I’ll see if I can track some down over here, it sounds like good stuff.
I add 30% water to my pva so it flows down smooth to the surface. It takes longer to dry but the results are better.
hmm i might just try that!
pva can give awesome results if you have the patience to spray it properly…
mould release waxes are generally made up of a combination of parrafin, silicone and carnuba. the different properties of each wax is dependant on the quantities of each in any paticular wax.
semi permanents are non transferring, as in they do not remain on the finished product contaminating the surface(think of painting). they are fast and foolproof.
the downside to spraying silicone is that it WILL transfer throughout the workshop in the air. if it comes into contact with reinforcements or infact yourself it can end up in a laminate causing weak spots begging to delaminate.
evodelta, the pva fisheyes on your waxed surface cause those two are a bit incompatible. if you want pva to stay put and just peel off afterwards, you have to apply a liquid wax, usually sold by the same company. you apply that with a cloth, and after about 1 minute you wipe it, not to a gloss finish, just to smooth out the lines, leaves a slight hazy surface, but the pva is what gives you the gloss. for a new mold, you apply that wax 6-7 times, and then you never bother again. just demold, wash the mold and spray pva again.
about spraying the pva, i spray it with a devilbiss airbrush, 1mm and about 1bar boost eehh i mean pressure.
pva is compatible with tr11o
Chill Aga, it’s an old thread, things have come on a bit since then. 
Although I did just recently find out you can get PVA in matt and gloss, just my luck that on the container I have it doesn’t say… I think it’s gloss, but when sprayed as a mist to make a mould it gives a matt finish which is the only reason I don’t like it.
On a similar note (as the thread title) we used silicone sealer like plasticene to blend the part we were copying into the flanges. We found it good in that it’s easy to apply (by gun), doesn’t stick to the mould at all, shiny, but is difficult to get smooth sometimes. It helped when squashing the plasticene in pushed the temp flanges off.
Everything went well until we changed to a different type of silicone, it reacted with the gelcoat which didn’t set wherever it was near it, we had to scrape it off, fill it back up and finish it off with sandpaper etc.
I’ll be trying to find exactly what the differences are…