Spray Paint Adventures and questions

[John G]

Hi,
I made some mdf coat racks for the kids, and so to get a good clean paint finish I thought I would spray rather than brush them. Other than with cans, I've never sprayed before, so this was always going to be an experiment. I ended up buying an airless spray gun (you know, those little electric ones), but in the end got very mixed results. I'm wondering if my results are normal, or if I did something wrong?

A) Thinning. I first primed the mdf with acrylic timber primer. I read elsewhere on this forum that acrylic works best with airless sprayers. The sprayer came with it's own viscosity testing funnel. The primer paint is very thick and gluggy, and I was very surprised how much I needed to water it down. About 50:50. Is this normal for acrylic paints? Or it this just airless sprayers? What do professional painters use when spraying the inside of a house - do they use commercial HVLP sprayers?

B) Coats. After watering it down so much, each coat of spray ended up being so thin I needed 3 coats of primer. I realise spray goes on much thinner than brush coats, but this thin?? Should I have used Flotrol instead of water, as I read here that it lowers viscosity without watering down the pigment as much as water does.

C) Overspray: I realise that with a thin, tree-like coat rack, there would be overspray. The trouble is, with a spray can you can get within about 10cm of the surface and still get smooth, gentle coverage, but this seemed impossible with the airless. The closest I could get was about 30cm, which obviously meant lots of overspray. Is there a way to make the spray more "gentle", or is this just the way airless works?

Thanks,
John.

[Master Splinter]

My experiences with airless spray have basically ended up with both the paint and the equipment in the bin for similar reasons. My take is that unless you pay top dollar ($500+) for your airless spray setup, it's pretty much a waste of time.

Buy a compressor and a sub-$100 gun - much better value for money than airless as there are so many other toys....errr tools... that need a compressor.

And ditch the acrylic paints, they are too much of a pain to spray. Note however, that enamel paint is sometimes called fairy floss, because it gets everything in the area sticky (so a good location is essential).

[Vernonv]

I'm with MS on most points. I've quite successfully painted lots of MDF with a compressor and cheapish HVLP gravity fed gun.

In regard to paint (and this is possibly where we differ), I've sprayed acrylic lacquer (auto paint), water based acrylic and enamels, all quite successfully.

Edit: one thing to be aware of when using water based acrylics is that (I've found) you need to really clean the gun thoroughly after each use.

[rogerjenkins]

Airless, ( electric ), spraying with water-based Acrylics can be, " a pain in the butt, " when you are a first-timer, believe me. I found THAT out the first time I used a Wagner Airless spraygun, & water-based Acrylic !
With practice, one can obtain quite a reasonable job,- But as forementioned it takes practice, and patience, same as with anything else in life !!!!!!!!!!!!

Thinning of water-based Acrylics is about 50% most of the time,- and another problem is that many strike is that they forget to continually move the spray unit in a left to right line,( or right to left as the case may be ), then wonder why they have got a big circular, " Blob, " of runny paint. Also it does pay to not jerk the trigger back in a hurry, but pull it on slowly, as by jerking the trigger switch, can send the spray nozzle off-target.
You will obtain over-spray no matter what type of paint you use, and worse, - the smaller the object,- the more the over-spray. You can, ( with practice ), get as close as 150mm. from the item to be sprayed, therefore suggest you spend some time with some scrap wood, and your spraygun, filled with water, ( Yes,- that is correct, " plain old-fashioned water !! ), and learn what you can do / can't do with it. This is the best way.
Suggest you set up a specified area as a Spray-booth, preferably somewhere that won't interfere with the rest of your workshop, or maybe if you have the backyard space, construct a separate small shed set up for spraypainting, complete with suitable exhaust fans, ( ordinary household fans blowing the air out through an open window, or door work quite well ), then you won't have to worry about overspray going everywhere.
Although I know of numerous Toy-makers who use ordinary GP guns, ( General-purpose guns ), & an air-compressor set to about 50lbs, an excellent alternative is a Touch-up gun, which holds approx 250mm. of thinned paint, and will operate on about 20 - 25lbs of air pressure,- but again, one has to take their time and to practice on some scrap material with thinners before actually coating any object successfully.

For the curious, although I have worked with spraypainting systems over the year, even worked alongside a professional automotive spray-painter when I was younger, ( & more energetic those days ), nowadays I simply use the old paint brush,- but I still take my time to get a good finish,- well most times anyway

Hope this info helps you.
Roger

[John G]

Thanks folks,
Yeah, I never expected to get awesome results with a cheap airless sprayer. But I thought it would spray a thicker layer each time.
I don't have a spray booth but I did mask off the spray area - I was just surprised how much overspray there was (compared to cans).

Does everyone just thin with water, or do you get better reults with floetrol?

If you really need to do heaps of coats over and over again (with cleaning and drying time in between) then it might be easier to just buy 10 cans of enamel spray - better results and no clean up!

I thought HVLP was good for painting fences, but not for fine finishes?

[Vernonv]

Does everyone just thin with water, or do you get better reults with floetrol?

Again my experience is not with airless, but I normally thin with water at about 10% of paint volume.

I thought HVLP was good for painting fences, but not for fine finishes?

I certainly haven't heard or experienced that. The beauty of HVLP is that you generally get less overspray and less paint wastage, because you are dealing with a lower air pressure,

[John G]

I certainly haven't heard or experienced that. The beauty of HVLP is that you generally get less overspray and less paint wastage, because you are dealing with a lower air pressure,

Or was it HVLP was good for paint but no good for varnishes, because the coats are too thick?

Either way, HVLP sprays thicker than other systems, right?

[Vernonv]

Either way, HVLP sprays thicker than other systems, right?

Not that I'm aware of. The amount of paint put down generally has more to do with gun setup, than gun type (HVLP or high pressure or whatever).