Getting a good finish on a plug?


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Alibro
Alibro
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Hi guys
For those of you how are experienced this is probably a stupid question but I'm gonna ask anyway as I suspect it is something many struggle with.
What is your technique for getting a good finish on your plug?
I have a GF part which I want to take mould from, this is it although I have worked at it since these photos were taken.




I wanted to make a copy of my cracked instrument binnacle but it was very textured so I smoothed it as best I could and made a mould from it (actually I made four as this was my
first ever go at doing this and I didn't really know what I was doing) I then made a GF part from the least worst of the moulds and set about smoothing it. I started with 120 grit, then went on to 400, 800 and 1200.
My plan is to take this part which apart from the scratches I am happy with and make a new mould in two or three parts (advise on this very welcome) so that I can make CF copies which I hope to sell.
I thought it was going well until I rubbed it with cutting compound to a nice shiny finish but when I looked closely it was covered in lots of scratches, probably from the last two grits.

So, do you wet sand or dry sand?
How can you tell when you have sanded away the marks left by the previous grit? I dried it and thought they were gone but apparently not.
Do you use a DA sander, a block or just hold the paper?
How long do you normally spend smoothing a part like this, I spent a whole evening at it and will probably need to spend another one to get rid of the fine scratches.
How smooth a finish is realistic on Gel coat?

Thanks in advance
Ali
Edited 11 Years Ago by Alibro
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Hanaldo
Hanaldo
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Yeh that's the curse of PVA. That roughness will be transferred to your mould and will totally undo all the work you've put into it. It is apparently possible to wipe on PVA and get a nice surface finish, but I never managed to achieve it. Spraying is the way to go, I suggest washing it off and waiting for the spray gun.

I use a standard 0.8mm nozzle on a touch up spray gun, and PVA is a breeze to spray. Just give it 2-3 very light dust coats, then 1-2 full coats. PVA has excellent self-levelling properties so it's possible to achieve a perfect smooth, glossy surface. When you're done, tip the unused PVA back into it's bottle and pour some water into the gun cup. Spray until it's empty, clean up done. I love PVA personally.
GO

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