PVA Issue

General Composites Discussions Composites Talk
#1

Ok so I’m full of issues. This ones a PVA one, haha.

I’ve wiped on my pva with a cotton ball before and it works ok. I’d rather spray it because it gives a better even coat. The FIRST time I ever sprayed it everything went on fine, but every time I sprayed after that when I spray I get A LOT of stringy stuff floating in the air. Almost like the pva is bouncing off the item and then drying in the air afterwards.

I haven’t changed anything, and now that I think about it maybe I’m shooting to close to the part but that’s the only thing I can think about.

The tempeture has varied on all the times I’ve sprayed from 60-80 degrees. I’ve been spraying at the same pressure 30psi and am using a 1.4 mm tip. It’s a satajet nr2000 gun I’m using as well.

Anyone else have this issue?

#2

Try diluting more, or use lower pressure.

Or quit using PVA…

#3

To be honest, for me pva is sh*t , you can use this for making no-detailed poliester stuff…

#4

I’ll try and dilute it. I’ve been pouring straight from the bottle into my gun. It’s stuff from fibreglast.com

I always thought you wanted to use PVA on a plug and on a mould but I’ll read up on some other stuff.

#5

only on bad plugs and moulds :wink:

#6

Haha it falls into both of those I think.

#7

In that case, PVA is the way to go.
The last time I used it (had to use it) I used it over a wax. Sprayed it on, wiped it off. I thought I wiped it clean, but when I demoulded the part there was a very thin layer of PVA still there. It was the best result I got so far using PVA, like it wasn’t there at all :stuck_out_tongue:

#8

I sprayed it over a towing tank model, with unknown paint on it. Had to make a polyester mould from it.

Also, on Gibco Flexmold it works really well.

And for making moulds of sanded objects. (once had to make trailer supports for a boat, and the boat was sanded with grit 80… Sloshed 2 kgs of PVA over it. Released perfectly…

Also it is great to “break in” a polyester mould. The first 2 products, use PVA. After that, switch to semi perm.

#9

Yeah I have dolphin wax and then pva. Guess I’ll be doing the perm release route.

#10

I would use it with a base of wax or semiperm, PVA gets sticky as hell. (like always: been there, done that :stuck_out_tongue: )

#11

Yes, you always need a base wax of some sort. PVA is not slippery…

#12

PVA does the stringy thing when sprayed in an ambient temperature that is too warm or the humidity is very low. Essentially the PVA is drying in the air before it gets to the release surface. The solution is to:

  1. Spray in cooler temperatures.
  2. Increase the humidity in the spray room (mist the room/floor with water using your spray gun)
  3. Add 10% water by volume to the PVA before spraying.
#13

Haha I just read your post on pva last night. They should make stickies for us new people.

I did everything but number 2. It fixed the issue!