Best time to apply next coat - spray lacquer

[Arron]

Hi. I've been thinking about the best time interval to observe between subsequent coats of lacquer. I use Wattyl Stylwood, and there is nothing on the can to indicate the correct interval. I think I read elsewhere that it should be in the region of about 30 minutes, at which point it would be quite dry. However it seems to me that the properties of lacquer mean that it is best recoated when still somewhat wet. I guess that would mean within 5 minutes or less of the previous coat being applied.

I'm figuring the advantages of recoating while still wet are that the subsequent coat would therefore meld better into the coat below, and the total mass would dry more slowly and have the ability to level out better. Obviously this doesnt include situations where you want to sand between coats.

Does anyone know the right answer to this.

cheers
Arron

[soundman]

Remember true laquers cure by solvent evaporation alone...yeh yeh there may be some crosslinking that occurs with the fullness of time, but the main issue is solvent evaopration.

Likewise all simple laquers will redisolve in the apprpriate solvent at any time.

These are two critical things to understand and there are swings and roundabouts.

This means that subsiquent coats will chemicaly key in because they partly redisolve the previous coat at any time.

one other thing is that if you stuff up big time, you can wipe the whole lot off with a solvent soaked rag rather than grinding it off with sandpaper.

AND there are all sorts of swings and roundabouts inbetween.

It is a reasonable practice to after fine sanding the final coat, to mist over the job delicately with thinner...that partly reflows the very top of the film and the fine scratches from the sanding disappear......be heavy handed and you have just taken 3 steps backward, because the whole film reflows.

Likewise, iff you have built up a good flat choked out finish and you lay up a heavy coat, all the existing film may reflow and all those airbubbles will start rising again....Oh yeh been there

Laquer is realy a very sharp tool, iff you are good you can get an extrordinary level of controll and realy fast results, if you are clumsy you will get cut.

A mate of mine who trained as a piano builder & restorer, reconed they could get 5 full coats of nitro on a piano in a day.

In good warm dry weather, a thin coat of nitro can be properly off in 5 minutes.....This is why it is used in manufacturing.......it goes off fast........in fact you will be looking for retarding thinner so what comes out the gun hits the job wet and gets a chance to flow out.

Start laying it up thick and in cool weather and it may take an hour or more to go off hard enough that ya don't leave finger prints in it.

The thing with spraying laquer is thn coats and lots of em.........the reason why is the reason you can.

And the drying time depends on the product, how much of what thinner you use, how thick you lay it up and the weather.

If you recoat too early you run the risk of dribbles..which is why you are using laquer in the first place..because you hate dribbles.

In my view the earliest you should reapply, is when you see that wet sheen go away..and that is a common practice with nitro.
Spray over and wait till that wet sheen has gone and the solvent has flashed off and go again.....on some pieces and in some weather you wnt even put the gun down......spray, spray, spray.....loooking, loooking, loooking.....there it goes......wait.....not just yet..... now spray agian.

Some call these individual slashes with the gun coats.....others don't...some documents talk of double or tripple header coats.

Better than one heavy coat.

cheers