T.S.Davis

Can I use my Paasche VL to apply PVA or am I asking for trouble?

davidfee

You will not hurt the airbrush with PVA. Wash it with soapy water when done, then rinse well with clear water. I've never tried spraying the stuff (I use an old T-Shirt), so I can't help there. I've heard that different makes of PVA, and even different batches of the same brand, can behave quite differently when sprayed.

Good luck,
David

winship

Yes. Just don't store the PVA in the gun. It will eat away at some metal parts especially aluminum.

I use a Badger and Thayer Chandler airbrush to spray PVA on small molds. Set the pressure at about 75 to 80 psi. The stuff loves to be atomized.

CoosBayLumber

My Feedback: (1)

WINSHIP:


How do you get the PVA to stop giving a dusty looking appearance when shooting with such high pressure?

I finally had to go to a touch-up gun and shoot at about 35-45 PSI. This left a glossy surface when done.


Wm.

SKYPYRO

I'm curious about that too, Winship. Using a Badger 350, I had to turn the pressure way down to about 30 PSI until it would go on wet. My PVA is the constistency of runny syrup, how's yours? Do you spray it on layer by layer like paints, or do you just soak it in one or two coats? Do you thin it at all?

Thanks,

Dan

jr branham

My Feedback: (2)

Terry,
I also spray mine on with an airbrush. I use the the Badger economy model single action brush. I shoot it on with higher pressures. I spray multipile coats. Let it dry, it will take longer to dry in the lower areas of your molds.It will change in appearance when it dries. Your shop temp and humidity factor in on drying time. Don't start lay-up until it is dry. Also don't touch it with your fingers or anything. After you pop your part, wash the pva off your molds with warm soapy water. After you pull several parts, you might possibly be able to omit the pva and just wax. I would try it on the hatch first since this is a part that is more apt to pop free from the mold than the bottom hull. Enjoy.
Jr. B.

winship

CoosBayLumber

Most of the parts that I have made have the flat finish instead of glossy. Wheel pants are sprayed with the PVA flat since they are going to be painted. Also adding cabosil to the PVA will give it a flat finish. PVA can also be thinned with water to help it level or flow out to a glossy surface although I spray mine out of the jug. The PVA that I have is pretty thin, closer to water than runny syrup. PVA will have some gloss but never like a mold that has been polished to a mirror finish. Speaking of mirror finishes I took a tour of a place that was making race helmets here in Indy. The molds were made from nickel plate. They modified the helmet until the desired shape was obtained and then sent it off to a nickel plater. The helmet was dipped repeatedly into a nickel bath until the desired thickness was obtained. This made for a great looking mold that was durable, metallic and shiny. The original plug would have to have the desired finish before the nickel dip started though.

IF going for the glossy look I keep the pressure up but pull the needle out to get more flow or material to the gun. When spraying I candle or bounce the light off of the surface to see if it is going on glossy or not. If spraying a mold that is cold or around 65 deg. F the PVA will level out more than if the mold is at 100 deg. F You are correct about the higher pressure having a greater tendency to spray flat. Since I am spraying at a higher pressure I just add more fluid until it matches the pressure. You have to keep the gun moving or you will tend to get runs but it sure goes on fast.

Some people don't like to wait for the PVA to dry. I will speed the drying time up with a heat gun but be careful not to heat the mold too much if it is a room temp mold. Let your hand overhang the mold to feel just how much heat the mold is getting or use a hairdryer instead.

SCALECRAFT

My Feedback: (13)

Winship

I assume one would wear a fine particulate mask if one mixes cabosil (fluft silica) with PVA. There would be a mist developing around the work area . It is not user freindly, is it?

Steve

winship

Cabot's Fumed Metal Oxides business is made up of two product families: fumed silica and fumed alumina. Free-flowing powdered fumed silica products include CAB-O-SILĀ® Untreated Fumed Silica and Treated Fumed Silica. CAB-O-SPERSEĀ® is fumed silica or fumed alumia that has been pre-dispersed in water.

Due to its versatile nature, CAB-O-SILĀ® fumed silica is used in a variety of products, ranging from spark plugs and printing inks to pharmaceuticals and cake mixes. In fact, Cabot customers fine new applications for fumed silica every day!

Cabot Fumed Silica is used to:
provide rheology control for liquids,
serve as a reinforcing filler in elastomers,
improve free flow of powders,
dry carrier for liquids and
emulsification agent.

The above was copied and pasted from the Cabot web page. If the stuff is good enough for cake mixes and some brands of ketchup (remember the comercial for the ketchup that didn't run?) I guess it is good enough for my PVA. A mask would be a good idea when spraying the PVA and cabosil in my opinion due to the PVA.