Matt Varnish Problem

[Alpineman]

Last night I sprayed the brake vans I am doing (previously sprayed with Halfords red primer) with Humbrol acrylic matt varnish to seal the transfers. When I looked at them this morning, the varnish has not dried clear but in places has left a transluscent pale bloom on top of the paint. It is very disappointing, as I had gone to a lot of trouble over the paint and fiddly little transfers, and the Halfords paint had left a perfect matt finish. Now the whole effect is spoilt, and I don't know what I did wrong. Can anybody suggest a reason please? (I did shake the can for 2 mins so it's not that).

I can't face painting and detailing them all over again, so the only thing I can think of is to try a weathered finish to hide the bloom. I don't really like "mucking up" something I've just spent hours getting just right, so don't normally do this. I did once try hazing some matt brown from an aerosol over a few wagons as an experiment, which gave a result a bit like Hornby weathering, so I could try that again I suppose. Does anyone have any other suggestions please?

Thanks

Steve

[jwealleans]

Hi Steve,

I had this problem with a pair of GE coaches a few pages back in my workbench. It was with enamel varnish rather than acrylic, but your symptom sounds the same.

I blamed it on the models being cold/damp when I sprayed them (my attic workshop gets very cold and damp in the winter). Models for painting go in the airing cupboard the night before, as does the paint. On this occasion one or other was too cold, was my diagnosis.

I left it a couple of days with the models in a warm dry place and then applied some more varnish. After a couple more coats the bloom had gone.

HTH.

[Alpineman]

HTH - Thank you - that is a distinct possibility. I did the spraying in the cold garage, because the family objects to the smell of spray paint about the house. Therefore, although the paint and wagons were at warm room temparature beforehand, the garage was cold and I left the wagons in there for half an hour until they were touch dry and could be moved.

I'll do as you suggest and leave them a few days before recoating. It can't be any worse than they are now.

Regards

Steve

[Mallard]

I know a very accomplished coach builder/ painter that has problems with some varnishes these days as they have a water content would you believe and can leave a 'bloomy' patchy finish!
If you go on RM WEB and contact "coachman" (not the above builder); he should have the answers re this.
Sincerely 36E

[Atlantic 3279]

I'd go for the "cold and damp" theory too, or possibly just too much thinners.

Not having a heated and force-ventilated spray booth (who does?), but definitely having a daughter who moans about paint fumes, my compromise for spraying oudoors or in cold outbuildings in "winter" is to get the models AND the paint thoroughly warm indoors, then nip out and spray, and get 'em back inside ASAP.

[mick b]

Never varnish when raining or its just stopped or about to start any time of the year. Another thin coat ot two should sort it. I had the same problem with halfotds Matt Black yesterday. Another coat and then a gentle warming with a hairdryer solved the problem

[Andy Hardman]

Sorry to hear about your varnish problem .

In my experience, its caused by-

1. Adding too much varnish in one go.
2. Using a thinners that drys too quickly - this forms a seal on the surface, and the varnish underneath does not dry correctly, causing a milky-white appearance.
3. Damp can be an issue.

When I spray enamels, I use Phoenix fast drying thinners, but never use this with varnish - I use ordinary enamel thinners, which drys more slowly.

Been there -done that - got the video

Hope that helps,

Andy


andyhardman.fotopic.net

[Alpineman]

I'm most grateful to everyone who has responded. However, I should say that the spraying was done with an aerosol, so I had no control over the thinners/varnish mix. It must have been the cold conditions and possibly too heavy a coat for those conditions. I'll know better next time.

Steve

[52D]

When spraying from an aerosol i was always told to shake well and also stand the aerosol in hot water to ensure good mixing and an even spray. This prevents the orange peel effect when spraying paint. After use invert the can and give a quick squirt to clear the nozzle.

DO NOT APPLY DIRECT HEAT TO THE CAN

[manna]

G'Day Gents

Here in Oz we have the opposite, try painting in 46c, dries on the brush so fast, go'es lumpy on the wall? Tried wall papering once on a very hot day the paste dried before I could get the paper to the wall, had to wet everything with spray bottles??

Railway room gets so hot I've had to fit an air conditioner, the expansion joints we're so big that wagons keep falling off the track
manna

[Atlantic 3279]

G'Day Bruce!

Well there's another perspective. A bit like the day my wife (or Sheila) started brush painting our lounge radiator whilst it was still quite warm, with some 'orrible "modern formulation" quick drying undercoat, and she failed to plan her painting to keep the wet-edge going. I had a lot of rubbing down to do after that.

[manna]

G'Day Gents
I know where your coming from lol. The one thing about big expansion joints the nice 'click' as your train go'es over it, but a heavy whitemetal loco, you get a 'clunk', sorry to get off topic Alpinemen
manna

[Alpineman]

The white bloom didn't fade, so I gently scraped off the worst of it with the tip of a scalpel. This has left a paler, slightly worn effect to the red oxide that doesn't look too bad to my eyes.

Steve

[52D]

I Wonder if you could have rubbed the bloom off with T-cut or similar compound.

[Alpineman]

It's a thought 52D, although I think the T cut would have tended to clog around the raised details and in the gaps between the planks, and been difficult to get out again.

Steve