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Old 08-20-2014, 04:13 AM   #11
Michiel

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Hi Dallas, i always infuse my part but i've been getting this print thru effect on my parts which i thought was due to the tack spray i'm using (Airtac2) but on the last part i infused i tried slowing down the infusion and i got way better results, no fabric print thru but i ended up with a few pin holes which i thinks were as a result of bridging on one of the corners.
You aren't getting print true with a slower infusion because the part has more resin in it. Pin holes also can appear with a slow infusion because of the big pressure difference and the air expents at the resin front.
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Old 08-20-2014, 08:18 PM   #12
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I really only care about pin holes. Believe it or not a quick sand on the part an good clear coat is all I ever do if I get print through. Print through can happen in the mold or in the oven or two years down the road. Heck some super cars have print through from the manufacturer. It's voids and pinholes I don't care for.

The op just seems like he needs to polish the tool a little better. Maybe just apply the release a bit better in my opinion. Other wise his mold is very very nice I must add!
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Old 08-21-2014, 07:39 AM   #13
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Mmmmm I would hold off on doing an in mold clear or gel just yet. Pin holes are a bear but... In mold sometimes traps them too. Then they are shiney little voids in the laminate.

Go ahead and compound your mold with 3m and then hit it with 3m machine polish. Wax twice with meguires then... Buff it off to a nice shine. Go to west marine and buy the purple pva they sell. spray one coat of pva on the mold reducing with a very slightly. Let sit over night and try again.

Brush on a generous even coat and lay your first ply. Then quickly dab the fabric down. Lay the subsequent layers by dabbing it into the carbon.

Peel ply breather and then your vacuum pad like you have. Shield the bottom of the pad with some bagging film so it doesn't wick resin.

You should be good. I get very few pinholes on my simple parts this way. I keep it simple.

The breather should clamp the carbon and draw the bubbles out as it wicks resin. Also..... Full vacuum can generate pin holes.

I stop looking for leaks when I can't barely pull my bag off the stackup when I wet layup.

Also.... I don't know why but a drop of black pigment per 2oz of resin makes my carbon shine much brighter.
This is what i have been using for a wax.
http://www.plasticareinc.com/Merchan...gory_Code=MRWC

The mold was wet sanded to 1500 grit then polished and waxed 4 times per the mfg's instructions. No PVA. I generally run full vacuum at this altitude which is about 25hg. Maybe pull less or less then more???
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Old 08-21-2014, 09:00 AM   #14
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I have not used that wax before. I use meguires mirror shine mold release wax. One buff and a single coat of pva. I also sand to 2000 and then compound and then polish by hand. I don't think vacuum is creating that hazy look I think it's the wax.
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Old 08-22-2014, 06:26 AM   #15
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Hi guys what's the real cause of fabric print thru and what precautions can one take to avoid such.

thanks in advance.
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Old 08-22-2014, 01:20 PM   #16
Michiel

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Hi guys what's the real cause of fabric print thru and what precautions can one take to avoid such.

thanks in advance.
A low vf ratio, the more resin the less print true. A coating is the best way to avoid it.
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Old 08-22-2014, 02:13 PM   #17
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Demoulding too early can also cause the fabric weave to show through the resin. Or, on say a part like a bonnet, if you don't post-cure and then the vehicle sits in the sun, this can also cause it.

Really I find post-curing is the best way to prevent any issues, even with a low(ish) vf ratio. Clear coat is the best way to fix the issue if it occurs.
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Old 08-26-2014, 08:29 AM   #18
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Quote:
Originally Posted by dallasb84 View Post
I have not used that wax before. I use meguires mirror shine mold release wax. One buff and a single coat of pva. I also sand to 2000 and then compound and then polish by hand. I don't think vacuum is creating that hazy look I think it's the wax.
So should I re-work my mold? What compound and polish do you use?

Any suggestions on a "after molding" clear coat to get rid of the pin holes?
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Old 08-26-2014, 09:53 PM   #19
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It really depends on what you want to do. I take my molds to 2000 because its easier to polish tight spots to a shine with compound. Just easier on the fingers.

Are you brushing a good coat in the mold first before you lay fabric down? You said you were wet layup right?
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Old 08-27-2014, 03:02 AM   #20
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It could be the wax but those swirls in the mould look more like sanding and buffing swirls to me. Just going on your pictures your moulds need a lot more work before waxing.
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