Patchy gloss with acrylic lacquer

[silentC]

I am spraying a full gloss Acrylic Lacquer. I started the job using lacquer thinners (Recochem in the purple tin 75% liquid hydrocarbon) but ran out after two coats. So the next day I went to the paint shop where I bought the lacquer and told him what it was for. He gave me a thinner made by the manufacturer of the lacquer (Concept paints - automotive paints). It's called Multi-thinner. According to the label is has 600ml/l Liquid Hydrocarbon and 400ml/l Ketones.

When I sprayed the next two coats, the gloss is a bit patchy on the sides and the edges are matt. The gloss after two coats the day before was much more consistent. As far as I can tell, the only differences in the set up are the different thinners and the fact it was 24 hours later and a few degrees colder with the subsequent coats.

Could it be the thinners? Concept Paints do make a thinner designed for this lacquer, which is intended for woodwork not cars, but it seemed to go OK with the Recochem stuff. Maybe I was lucky. What difference would there be in the thinners that could cause this, or do you think it was something else, like the temperature?

Hmm, actually, come to think of it I put the 1.4mm set up on the gun instead of the 2mm which I used the day before. Maybe that's it?

Any tips before I waste any more lacquer?

[durwood]

Always use the thinner for the productif you can. the acrylic thinner for acrylic lacquer is different to that of multi purpose thinner.

As stated your thinner is a multi purpose thinner meaning it will mix with different materials, in lacquer work that probably means the primer and any other associated products. Its usually only used by people who don't want to invest in the extra cost of buying the different thinners for each product. Its usually cheaper than the correct thinner, I only ever use it to wash up after spraying.

In automotive use the thinner is altered by the companies to a winter or summer mix to adjust to the difference in temperatures that one sprays in during the seasons. Results can be inferior if the wrong season thinner is being used. Usually its only the gloss level and drying time which is effected, if you allow the acrylic lacquer to dry for about a week you should be able to compound it to a full gloss, if you leave it for less time it may be too soft to use a machine buff on but hand compounding can usually be done 24 hours after if you need to do the job quicker. AL takes 30 days to 3 months to dry completely depending on the temperature and the application technique used.

Multi purpose will mix with the top coat but you will get inferior results which is probably what you have had happen. The different set up will make the air ratio different giving you a finish that is probably drier ( more sandy/rough) rather than just low gloss.

If the temperature is too cold (below 15 C ) you will probably get a blushing of the clear. this will give you a duller finish also. In bad cases the lacquer will go milky a few seconds after you lay down the clear.

[Ironwood]

I'm definitely no expert, but the first time I sprayed lacquer I used my 1.7mm gun, and got a patchy looking result, couldnt keep a wet edge.
Spoke to the guy at the paint shop about it, he recomended using a 2mm gun.
I already had one, so went home and tried it, results were much better, I could easily keep a wet edge and get a good looking gloss finish.

[wheelinround]

I am using my experiences with spraying bus and coaches were we had a similar situation 3 vehicles sprayed using the same paint one was using a different type newer thinners. to had gloss coats the third with the new improved thinners was dull. A dry looking finish turned out the thinners was what was termed OFF by the paint company incorrect mixture.

We got the 3rd vehicle sanded and resprayed buy company reps for nix. I have seen the same thing happen in mixing older tin and new thinners same type etc but needed to top up had done this a few times before.

[silentC]

OK thanks all. I'll get them to order in some of the correct thinners (seems a bit silly to stock the lacquer and not the thinners, but the guy who runs the place is a house painter and knows his stuff with house paint but doesn't have much of a clue outside that).

I ended up leaving it a couple of days and hand rubbed it back then buffed it with 0000 steel wool and paste wax. Came up OK, good enough for this job. Handy to know for next time though.

Cheers.