02GF74
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| posted on 24/10/06 at 01:45 PM |
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fibre glass release agent
I read the stuff to apply to a mould is pva release agent - that is different to pva glue, yes?
How do you apply it so you don't get brush marks?
Can it be sprayed on with a spray gun, and what sort of thickness?
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balidey
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| posted on 24/10/06 at 01:48 PM |
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Its very different stuff to the glue.
I dab it one lightly with a soft sponge. The layer is very thin, fractions of a mm. So thin that you get hardly any imprint into the gelcoat face.
Some people spray it on with a demister, like the Mrs uses for her hair spray.
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emsfactory
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| posted on 24/10/06 at 01:49 PM |
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You only need a thin coat. What are you releasing? you may net need it at all.
Blue is better for hard pulls. You can pour warm water into the mould to melt the blue and ease the lift. It is not needed for easy pulls.
If spraying you have to do it at a higher pressure than you would paint or it will froth.
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02GF74
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| posted on 24/10/06 at 01:54 PM |
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I'vre got one of the hand insecticide spayer things so that sould work?
I think I am going to make some cycle wings. I say think since I have laid down the papier-mache for the mould - will see if it retains is shape when
dry - may need some grass fibre reinforcing.
I'll probably have to paint/varnish the inner surface to make it less porous so may end up with brush marks anyway - as I am not sure if the
release agent will work on papier mache?
As long as I can get a reasonable finish I can sand the top down - these are SVA wings so don't need to be perfect.
(I know it sounds bonkers but you won;t be laughing when (if) it succeeds!)
[Edited on 24/10/06 by 02GF74]
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emsfactory
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| posted on 24/10/06 at 01:56 PM |
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quote:
Originally posted by 02GF74
I'vre got one of the hand insecticide spayer things so that sould work?
I think I am going to make some cycle wings. I say think since I have laid down the papier-mache for the mould - will see if it retains is shape when
dry - may need some grass fibre reinforcing.
I'll probably have to paint/varnish the inner surface to make it less porous so may end up with brush marks anyway - as I am not sure if the
release agent will work on papier mache?
As long as I can get a reasonable finish I can sand the top down - these are SVA wings so don't need to be perfect.
(I know it sounds bonkers but you won;t be laughing when (if) it succeeds!)
[Edited on 24/10/06 by 02GF74]
To each his own.
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balidey
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| posted on 24/10/06 at 02:11 PM |
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Easiest way to mould from that would be to reinforce it to keep its shape, bits of wood to brace it would help.
Then go over the top with body filler. Sand it to shape and get smooth. Then spray paint over that. Black helps you spot and bad or high points. Then
sand smooth. If you are only making one off the mould then sponge on the PVA. put plenty on, its still very thin. Then put a nice thick layer of
gelcoat on, as you will almost certainly want to sand it down afterwards and then you won't go through to the fibres.
As a word of caution, if this is your first GRP project, try making somthing esle first, an ashtray, or a blob of some sort to try out the technique.
That way you won't ruin your original pattern.
Also, the fumes do help to make your parts look better
[Edited on 24/10/06 by balidey]
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marcjagman
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| posted on 24/10/06 at 02:20 PM |
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What's wrong with using the wax?
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02GF74
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| posted on 24/10/06 at 02:25 PM |
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quote:
Originally posted by marcjagman
What's wrong with using the wax?
what wax? - please tell me more (my first time making moulds, as you can probably tell  )
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balidey
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| posted on 24/10/06 at 02:32 PM |
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If you are only taking one part off, then forget wax and use PVA. If you are making more than 2 then use release wax, and lots of it. Put on a layer,
then buff, repeat 10 times. Then admire the glossy face, then only need one re-wax between every other lay up. But unless the face of your mould is
very good to begin with then you are wasting your time. PVA is a quick fix, but it is a good quick fix.
As i said, practice on something, you will learn so much more by doing it than reading our comments.
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02GF74
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| posted on 24/10/06 at 02:38 PM |
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quote:
Originally posted by balidey
If you are only taking one part off, then forget wax and use PVA. If you are making more than 2 then use release wax, and lots of it. .
Damn, so what do it do if I am making exactly two parts?
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balidey
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| posted on 24/10/06 at 02:43 PM |
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Fibreglass i can do, counting i struggle with. For two i would use PVA.
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Peteff
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| posted on 24/10/06 at 03:43 PM |
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What's wrong with using the wax?
It wants seven coats and leaving to harden for two months The stuff i got from Joel looks like ink, I haven't used it though.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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antonyg
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| posted on 24/10/06 at 06:00 PM |
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have a look a CFS website the have a PDF that details fibreglassing
http://www.cfsnet.co.uk/methods.html
i used the stuff that looks like ink and it worked well
Thanks Antony
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