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#1 Dopes and O Rings

Posted: Fri, 03 Aug 18, 04:38 am
by bernomatic
I found that using the Brodak dopes was deteriorating some of the O- Rings in my Master Air brushes. I wonder if the more expensive airbrush brands use a more resistant O ring.

I ordered some chemical resistant replacement O-rings from Mcmaster-Carr. I'll give a report on the results when I get to do some painting.

#2 Re: Dopes and O Rings

Posted: Mon, 13 Aug 18, 05:31 am
by bernomatic
Did some painting of the USS Andromeda, here are the results.

Sprayed Insignia White Brodak Dope diluted at two parts paint to three parts thinner. In this instance the thinner was a 50-50 mix of MEK & Xylene.

I was spraying with a Master E-91 Single Action, external mix airbrush and I used a Chemical-Resistant Low-Temperature Fluorosilicone O-Ring to replace the O-Ring in the needle assembly and the air tip. McMaster-Carr doesn't carry the exact same size in that particular substance, so I tried a slightly larger (read thicker) O-ring for both replacements. I tried fitting (at great expense, more or less) smaller and larger sizes, with the smaller breaking while being fitted and the larger not allowing the Fluid Cap to thread. The o-ring I ended up using sheared off the excess while still maintaining a remnant o-ring which I decided to see if I could use. The incorrect size o-ring on the air tip just squeezed onto the airtip bushing with no observable detrimental effects.


#3 Re: Dopes and O Rings

Posted: Fri, 17 Aug 18, 17:38 pm
by bernomatic
To make a long post short, the o-ring for the needle assembly was completely missing when I broke the airbrush down to clean it. At one point while using it, I did note a blue speck land on the rocket which was a part of the o-ring. I am not certain if the complete disintegration was due to the thinner itself or the lack of integrity of the o-ring by being sheared by the needle cap. I know I should have taken pictures.

I did clean the airbrush with a standard o-ring (water/steam type) in place on the needle assembly. I used a 35% MEK, 35% Xylene and 30% Acetone mix to shoot through the airbrush to clean it. I noted no deterioration of this o-ring. Of course this one did fit better and was intact when placed.