[kiwichris]

More of a wood finishing question...

I've made up two nightstands from mdf, and sealed & enamelled the first with a brush, but thought I'd spray the second..

I picked up a cheap spray gun for the compressor but I hit a glitch...

The sealer was basically drying inside the nozzle of the gun.

This is one of the really cheap ones that runs the air constantly and the trigger only opens the venturi for the paint.

So, my question is: would a decent gun handle thinned water based primer better, or should I stick to a brush. ?

For the record, cleanup was a pain as well and for the size of job I'm likely to do I think a touch up gun might be a better bet anyway.

Cheers, Chris H

[ger21]

Exactly what kind of paint is it? If it's latex, you usually need an airless sprayer, due to the thickness.

[kiwichris]

Hi-ho,

It's an acrylic wallboard sanding sealer, I'm too cheap to use latex based primer. :-)

I thinned it a wee bit with water to spray as its quite thick. Coverage was good and it's worked well on the mdf edges. Problem was that I had to clean the nozzle out twice during the job.

I suspect the constant airflow was drying the paint in the nozzle of the gun.

Cheers Chris H

[ger21]

There shouldn't be any paint for the air to dry. My guess is it's too thick to spray with that gun.

[kiwichris]

Hmmmm.

I'm definitely thinking it's the design of the gun then. It was after all a whole $10. No expense spared. :-).

The venturi is internal and there is a 'dome' over top of it with a slit that creates the fan.

It's on the inside of the dome that the dried paint buildup occurs while using it. After 2-3 minutes the fan collapses to a 'squirt' and causes instant runs.

I've only ever looked at good quality guns from a distance but I'm assuming that the venturi is probably external, and the 'prongs' out the front create the fan by blowing air at the 'cone' of paint coming out the venturi?

I might have to have a look in a shop during the week and maybe get me a decent gun to try, I can just right off the cheap gun to learning.

Cheers, Chris H.

[ger21]

I've got an old Wagner HVLP gun that sounds similar. I spray a lot of water based polyurethane, and I get a lot of buildup where the finish comes out. I keep a damp towel and wipe the tip every 5 minutes or so to prevent buildup.

[Mountaincraft]

As a (hopefully ex) remodling contractor, I've never had good luck with those wagner style sprayers... they seemed to be more trouble than they're worth and end up wasting more paint than they got on the wall...

For large surfaces (like a room) I eventually went with a pro airless (which 'still' needs to be thinned with most paints) and never looked back, or for the smaller wood stuff, I've been brushing on the first coat, sanding and then spraying one or more coats (sometimes additional sanding) with an air compressor and automotive type sprayer (which still requires thinning)..

[Mountaincraft]

kiwichris, how big are the surfaces you are trying to paint?

[kiwichris]

kiwichris, how big are the surfaces you are trying to paint?

Hi..

Not that big in the scheme of things, just a small nightstand, 600mm high, 400x400 wide/deep with a shelf and one drawer.

I'll want to do larger things at some stage, but for the moment it's all in the name of learning. Coming from an Electrical engineering and IT background and turning my hand to making furniture is a bit of a leap.

Cheers, Me.

[Mountaincraft]

Do you have an air compressor?

If so, I'd try an automotive style sprayer...
'old school'
:cheers:

[kiwichris]

Hi...

Yeah, this one is an air spray gun, just a particularly cheap job.

I stopped into a large tools place on the way to work this morning and picked up a better gun with the venturi external so I'm picking that will be a lot better.

It's also gravity fed so I wont waste as much paint on the small jobs I intend to do with it.

Will be a couple of days before I can try it out but it certainly seems to be a better bet that the very cheap-o one started out with.

I'll post some pictures tonight what what I mean by the venturi being internal, I'm not sure the description is doing it justice.

Cheers, Chris H.

[Mountaincraft]

yeah, I'm not really understanding what you mean by internal vs external venturi...

[kiwichris]

Photos to explain. :-)

The 'Good' photo is the better gun I got, the venturi that picks up the paint is on the 'outside' of the gun and the air blowing in from the sides creates the fan pattern.

The 'Cheap and nasty' shows the one that I got first, not knowing it was junk.

The venturi is in behind the wee dome, and the fan is created by the split in the dome. So a percentage of the paint gets caught up behind the dome and the air rushing through dries it really quickly. It's basically a crap design. Blocks quickly and is fiddly to clean.

Before this I'd only ever used a 'badger' style modelling airbrush and spray cans. Live and learn.

Cheers, Chris H.

[kiwichris]

For the record....

The 'good' gun was much better. Didn't block and much easier to clean.

I was concerned that my small compressor wouldn't keep up (2hp) but it was fine running at 50psi.

I thinned the paint 1:2 with water (1 part water) and it seemed to work well, although I need to do a bit more playing to get the best results.

Quicker than a brush and a better surface to boot. Just what the doctor ordered for sealing mdf as its a painful process. :-)