Varnish spraying - Warning - opaque glazing

[Noel]

Just a word of caution if spraying varnish either from an air brush or using a rattle can aerosol. Strongly recommend not spraying in the same room as other model rolling stock otherwise there is a risk the glazing on the other stock may go opaque. Using an air spray booth with a fan that ducts the air to the outside may avoid this. This happened to me recently when the glazing on a loco and a coach eight feet away from the area I was spraying varnish both opaque on the side nearest the work bench. This was obviously caused by convectional air currents in the room that carried suspended varnish in the air. You live and learn! Recently when doing the 121 and C class locos I used an outdoor area to prevent a repeat.

[Broithe]

I recently rescued an old-style cooker hood from a kitchen make-over, with the intention of constructing some sort of small spray-booth affair with it.

 

 

I have opened up a similar one before, to fix it, and the motor was an induction affair, with no brushes to give cause for concern over igniting solvent vapours. I'm hoping that I find this one to be the same.

[Glenderg]

Just a word of caution if spraying varnish either from an air brush or using a rattle can aerosol. Strongly recommend not spraying in the same room as other model rolling stock otherwise there is a risk the glazing on the other stock may go opaque. Using an air spray booth with a fan that ducts the air to the outside may avoid this. This happened to me recently when the glazing on a loco and a coach eight feet away from the area I was spraying varnish both opaque on the side nearest the work bench. This was obviously caused by convectional air currents in the room that carried suspended varnish in the air. You live and learn! Recently when doing the 121 and C class locos I used an outdoor area to prevent a repeat.

 

I don't think convection currents are to blame. In 8 years of spraying, even with all windows closed, I've never seen this happen, nor heard of it happening from anyone in the respray community.

 

If you're using a 0.5mm nozzle with the needle pulled back to open out the nozzle, the "blunderbuss" technique, maybe then.

 

Are you sure it isn't glue fumes inside the stock that's caused it?

 

Anyway, the fix is to get a jobby of brake fluid and using a small 000 brush, coat the glazing only. After twenty minutes you should have clear glazing.

 

Make sure it doesn't touch other paintwork though.

 

Humbrol make a clear gloss varnish that will restore glazing to clear, designed for aircraft canopies on models that have gone cloudy.

 

HTH

 

Richie

[Glenderg]

I recently rescued an old-style cooker hood from a kitchen make-over, with the intention of constructing some sort of small spray-booth affair with it.

 

[ATTACH=CONFIG]27773[/ATTACH]

 

I have opened up a similar one before, to fix it, and the motor was an induction affair, with no brushes to give cause for concern over igniting solvent vapours. I'm hoping that I find this one to be the same.

 

Nonsense, but if any man can make it work!!!

[Noel]

I don't think convection currents are to blame. In 8 years of spraying, even with all windows closed, I've never seen this happen, nor heard of it happening from anyone in the respray community.

 

If you're using a 0.5mm nozzle with the needle pulled back to open out the nozzle, the "blunderbuss" technique, maybe then.

 

Are you sure it isn't glue fumes inside the stock that's caused it?

 

Anyway, the fix is to get a jobby of brake fluid and using a small 000 brush, coat the glazing only. After twenty minutes you should have clear glazing.

 

Make sure it doesn't touch other paintwork though.

 

Humbrol make a clear gloss varnish that will restore glazing to clear, designed for aircraft canopies on models that have gone cloudy.

 

HTH

 

Richie

 

Thanks for the tips Richie. I was using a humbrol acrylic matt varnish rattle can with an air spray booth which had a fan and filter unit, but NOT ducted to the outside (i.e. only through the filter). In addition to that I had a little fan heater running at the back of the room about 10ft away which may have assisted an air current moving the vapour after it passed through the filter. I guess these filters are fine for collecting paint particles but not so good at collecting airborne solvents. I assume had I a duct to the outside there might not have been a problem.

[Riversuir226]

Never heard of it happening, I've sprayed everything from acrylic to car paint and I've never had an issue with this.

[Broithe]

It may be the recirculation that is at the root of the problem.

 

Where did the 'extracted' air emerge? And in what direction?