Spraying question for Allen

[56nortondomy]

Hope this is not too stupid a question. After watching your tutorials on spraying, one thing you don't mention ( unless i've missed it ) is do you need to clean the gun in between coats, seeing as they are only 20 to 30 minutes apart? Also does Mirotone have a shelflife? I have some that i've had for about 2 years Wayne

[Allen]

I don't clean the gun even between spraying instruments months apart. The gun that I've used for instruments just got a birthday clean up only because the lid was getting too difficult to remove because of the build up after 6 years. The internals were fine.

Lacquer doesn't go off in the gun like catalysed finishes do. Those you have to clean out after each session. One reason I still use lacquer on instruments. I have to clean enough guns every day at work. The last thing I want to do is the same thing when I'm suppose to be enjoying my hobby/work at home.

[needsmorecowbel]

Allen I witnessed the ridiculous amount of mdf dust that is thrown around when you use a router to make a radius dish. Should have heeded your warning and used Graham's simple technique. The only thing I didnt understand with his technique is how to cut the curves for the pine chocks under the 3mm mdf dish or are the chocks just triangular? I don't have a bandsaw or a circular saw at the moment so cutting them accurately was impossible. Only had the router and some pine so the old routing technique was used. So...Much...Dust...

[56nortondomy]

Thanks for your swift reply Allen, i probably would have run some thinners through the gun after every coat, but not now.Thanks again regards Wayne

[Allen]

I've not used Grahams method for a radius dish, but I believe that the wedges are just triangular and that the 3mm ply will smooth out into a curve when pressed into the shape.

[liam_fnq]

I pattern routed the wedges for my dish. They were cut with the required radius ie. not straight. I'd be suprised if that worked. The 3mm mdf top was glued with go bars.

[Nick]

The one I made, I just bandsawed the radius out of the ribs & cleaned up to the line on the belt sander. I just pulled the 'dish' down (5mm MDF sheet) in the centre with a woodscrew (after applying glue as well). I seem to remember documenting my dish build but it got lost in the great crash of 0 10.
Back to the Original Post, Wayne. I don't clean between coats either, as Allen said, it's amazing how long the stuff stays in the gun without 'going off'. I was like you when I first started spraying & was worried about it & used to apply one or two coats twenty minutes apart then clean the gun, let the finish dry, sand then repeat procedure. Needless to say I soon got sick of this despite my enthusiasm for a new process! The only time I'll clean the gun 'properly' now (i.e. strip it down completely & soak the parts) is if I've been spraying a colour & am going back to clear or changing colour where I don't want any contamination. Usually I'll just empty the bowl at the end of a spray job & leave a small amount of thinners sitting in the gun.

[graham mcdonald]

Re: radius dishes

You should cut the slats/ribs to the radius of the dish you want. A bandsaw is really necessary, although it could be done rather tediously with a coping saw (?) The curve doesn't have to be precisely accurate, though the more accurate the better. On a 60cm/24" dish the slats are around 10mm thick at the edges down to around 5mm thick in the middle. I just got some 2x1 pine, cut 30cm lengths, traced the curve on the side so the thickness at each end were the same and cut them out. I sand saw marks out with a orbital sander, mostly to make sure the thickness of the slats where they meet in the middle is consistent and then lots of glue (titebond or even white PVA) and glue on 3mm mdf with a bunch of go-sticks. Very simple, quick and as accurate as you need

cheers

g

[needsmorecowbel]

Cheers guys sorry to partially hijack the thread.

Stu

[Gizmo]

Usually I'll just empty the bowl at the end of a spray job & leave a small amount of thinners sitting in the gun.

This is my recommendation. There is no problem with leaving lacquer or shellac in a spray gun overnight, but the way I do things sometimes the overnight will stretch to a week or a month . It also depends on the materials your spray gun is made of. I have a good quality gun I can leave lacquer in indefinitely as Allen says, but I also have a gun with a brass pick up tube that turns green from lacquer after a month or so, and a touch up gun with an aluminium cup that shellac will corrode within a week. Don't ask me how I know, I just know.

[56nortondomy]

Thanks Allen, Nick & Gizmo, i won't worry about cleaning in between coats now, which is what i would have done before your advice, so that will save some time and i'll be able get other things done. Thanks again Wayne

[nnickusa]

What size nozzle do you use on your gun for Mirotone, Allen?

[Allen]

Use anything form 1.2 to 1.4mm

1.4 is pretty much standard for most fine finishes. I crank the fluid control know in 2 full turns on a 1.4mm tip.

[Ormsby Guitars]

2k, the gun gets cleaned after every usage.

Nitro, the gun is left with whatever it has in it left over, and not touched again until I need to spray again. If Ive finished a guitar (last coat), i'll maybe chuck 100-200ml or so of thinner in there. Ive left a nitro gun up to three months without using it again, and never had one clog/dry/splatter/etc.