Mould problem with PVA Release Agent


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+cosworth
+cosworth
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I have a problem with pva mold release agent, put the pva with a clean lint-free cloth
but when dried pva is not uniformCrazyout spots where there is thepva?
This may not clean the mold?


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Joe
Joe
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Hey,

Well if you are SURE that u went everywhere on your mold with you pva impregnated cloth, pva IS there even if you dont especially notice it. In some areas you could have a thicker layer than on other areas, thats why you may not notice it everywhere. This is especially true with darker mold gelcoat colors. Try to always have a powerfull light above your mold and move your head around your mold, so you can see the pva "wetout" as you apply it.

If you were tempted to redo a second coat of pva before full cure of the first one, you may have removed pva on some spots. 

If my opinion is worth something (:WhistlingSmile, lint free rags are maybe not the best way to apply pva. i use soft foam little cylinders and that works great. I think these foam stuff are from paint supplies. They are 3 cm diameter by 3cm long, so I can clearly see what i'm doing rather than have a portion of rag obstructing view. Plus they release the pva in a consistent way. And they last waaay longer than rags.

If you have fish eyes, well, its another story. From my little experience, the only time I had fish eyes was when i did not clean the wax properly, too much excess was left. You could see the "lines" of wax even if it did not feel with the hand.

Also, if your polishing compound is containing silicone, it may mess wax and pva.

Other than that, I dont see why you would have a problem, but more experienced people will certainly tell you.

 



 


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Paul (Staff)
Paul (Staff)
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Hi,

I second what Joe has said about application method, and how it can somtimes look like it's not coated an area when it has...

There is also a neat little trick that you can do to stop the PVA from beading off or 'fish-eyeing' on a waxed mould surface; just add a little (less that 5%) washing-up liquid too the PVA this lowers it's surface tension and reduces the problem, I have never found it to effect the performance of the release, it does however take a little longer to dry.

Let us know how you get on.

Paul Statham
Easy Composites / Carbon Mods - Technical
Joe
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Paul (Staff) (24/01/2012)
Hi,

I second what Joe has said about application method, and how it can somtimes look like it's not coated an area when it has...

There is also a neat little trick that you can do to stop the PVA from beading off or 'fish-eyeing' on a waxed mould surface; just add a little (less that 5%) washing-up liquid too the PVA this lowers it's surface tension and reduces the problem, I have never found it to effect the performance of the release, it does however take a little longer to dry.

Let us know how you get on.


Muhaha nice little trick !!

 



 


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