Spray gun advice ...

[Arfa Daily]

I have a project coming up later in the year, that will involve getting a reasonably nice paint finish on some metal. Having a half-way decent compressor, and spray guns being cheap, I though this might be an opportunity to get a gun, and give it a go. Trouble is, I don't know what sort of gun to go for.

As far as I can see, there seems to be two basic flavours : Suction feed, and gravity feed. I'm inclined towards a gravity feed, just because it sort of 'feels' right - not that I've ever actually held one, if you see what I mean ... Also, I've seen Rick on American Restoration using one. Trouble is, I don't seem to be able to get a definitive answer from anyone on what is the most appropriate use of each type. It always seems to be a bit of a

"Hmmm, well ... it depends, you see ..."

"Errr, yes ... ? On what exactly ...?"

Well, for some jobs one is better than the other, really ..."

"Errr, yes ... ? So which would you use for which sort of job ?"

"Well, it depends, really ... "

And so it goes on in ever decreasing circles :-\

So what's the story ? Is it just whatever feels comfortable, and there's not a lot to choose between either basic type ? Looking at f'rinstance Toolsatan they have 27117 and 55471, both suction and the second a tenner dearer than the first, and then 70796 and 14021, both gravity feed, and again, the second a tenner dearer than the first.

I am confused, Anyone with genuine experience care to enlighten me ? :-)

Arfa

[Dave Plowman (News)]

I've done a bit of spraying over the years - cellulose on cars. And a decent gun and compressor ain't cheap. You'll also need an air drier, as blobs of water tend to ruin a finish.

To be honest, something like an Apollo HVLP spray set is probably cheaper. I have one and am happy with it. Cost about 200 quid. The turbine gets used for other things too like blowing water out of pipes when doing a solder repair.

That's not to say a high pressure unit isn't ultimately better - just *a lot* more expensive. A decent gun will cost about the same - and as I said you also need a good clean supply of compressed air that most domestic compressors can't manage.

[Steve Firth]

Well... it's probably weird prejudice but I prefer gravity feed to suction spray guns. And there's really not a lot to choose between them. Technique and practice count for a lot. I'd start by spraying scraps of plywood and possibly random lengths of wood screwed to the plywood to get the hang of it first. That way you learn how to set up the gun the way you want it to work. You also get a feel for too close, too dilute, too far away and too low a spray volume and what that means in terms of finish.

[fred]

I have an Earlex HVLP sprayer which I find easy to use as it has minimum co ntrols. Less bounce back and misting also, in my hands anyway. I found, wit h compressor operated units, that by the time I had finished faffing about with pressures, air volume, nozzles etc I would have had the job done with a brush with less cleaning up to do when finished.

[Dave Plowman (News)]

Fine if you're happy with the finish a brush produces.

[fred]

No problem getting a superb finish with a brush and without the risk of getting that jammy/treacly look that a too heavy spray coat can give.

Good brush, good paint/varnish, and go down through the abrasive grades.

[Dave Plowman (News)]

All you're saying is you don't know how to spray.

Quite. Sanding out the brush marks is far more work than the light flatting needed between spray coats.

Plus the fact that many brushing paints can't be flatted then polished in the same way as spray paints can.

[Dave Plowman (News)]

It is possible to get very good results with rattle cans - provided you do enough coats. They tend to apply a rather thinner layer than a proper spray gun. But for a one off still going to be a lot cheaper than buying decent spray equipment you might not use again.

[fred]

If you are sanding out brush marks you are using bad paint. Good paint appl ied correctly has flow characteristics that allow it to self level. There i s no earthly reason why it cannot be flattened and polished

(The problem I had with water based paints was that they dry too quickly be fore they flow out completely, or the ones I tried did.

And I can cut in cleanly so no need to spend time masking off and removing the masking tape afterwards and praying it doesn't destroy the nice clean e dge.

And I can clean a brush in about 2 minutes or even leave it wrapped in clin g film for a short while if I'm taking a break. Cant do that with any spray gun I ever used. At a minimum they need a blast through with gun cleaner w hich means finding some where to do that

And when I've finished with the paint I just replace the lid on the tin. No faffing about cleaning out pots etc.

Incidentally I've been using a sprayer for years. Used to work in the indus try.

[Dave Plowman (News)]

Which types of brushing paint can be flatted then polished afterwards?

That quote from you suggests not.

[fred]

Any decent oil based paint can be flattened and polished once dry. I have g one down progressively to 800g wet and dry silicon carbide paper on panel d oors and got a very high gloss finish without polishing.

There is no earthly reason why any oil painted surface can not be polished. I've done it with car cutting compound. Lot of trouble. Not worth the effo rt to my mind.

Au contraire, because of my experience, though many years ago, I do know wh at I am talking about. Unless I have a large surface to finish I don't both er with any spray equipment for the reasons given. Too much faffing about. Even to paint a fence it requires laying down dust sheets to protect the ar ea in front of the fence whether its grass or tarmacadam and then one has t o be aware of overspray and the neighbours, not on a windy day etc. None of these things are a problem if using a brush

If finishing a piece of woodwork and I want to spray it, and I do have HVLP equipment, I have to set up a temporary spray booth and am limited to wate r based finishes not having the proper spark proof extractor fans etc.

I often resort to spray cans from B&Q. Might take a lot of coats but cuts o ut all the above faffing about.

[Dave Plowman (News)]

Read the original post. The question was about getting a good finish on metal - not slapping some paint on a skirting or fence.

[fred]

You are long enough in the tooth to know that threads develop and get away from the original discussion, which is what this thread has done. It has de veloped into a general discussion on the pros and cons of spraying versus b rushing. You have in fact been indulging in this developed discussion so it s a little late not to mention disingenous (

to try that one on now.

[stephen.hull]

You can do this to a certain degree with Alkyd resin based paint, but you can't use the same polishing methods that you would use on a modern car finish as Car paint finishes are a completely different composition altogether.

Synthetics need a completely different technique as regard to polishing.

Stephen.

[stephen.hull]

[snip]

Not necessarily as that would depend on the type of paint used obviously, there are not many modern paints that actually flow out properly.

Water based paint does not flow out like conventionional oil paint.

Stephen

[polygonum]

I have found (on occasion) that adding a very small amount of water has made water-based paints much more pleasant to use and gave a better finish.

[fred]

I find this to be untrue. Car polishing compounds are predominantly very fine abrasives. So the composition of the paint is not really relevant.

Besides what is this talk about synthetics ? All paints are synthetics. The difference lies in the medium used to hold the pigments.

[fred]

WHAT ??

Not many modern paints flow out properly ? You are taking the mick or know not of what you speak

Which is what I said.

[stephen.hull]

[snip]

I beg to differ..........

The composition of the paint IS the point and it is also very relevant. You can polish any paint surface but you can't expect to get the same results on an oil based finish by used polishing compounds used in the same way as on Acrylic, Cellulose or two-component paints.

Oil paints are not designed to be polished, they are either gun or brush finish, but you may be able to polish certain Alkyd based oil paints only if its main component is Alkyd resin because its actually the hard resin you polish, unlike car finishes the above synthetic type paints form a skin that cannot be polished as you would expect to do on a conventional car paint finish.

Generally a synthetic (oil paint) is not soluble in its own solvent whereas car finishes are, you can use the same pigment yes but the solvents and medium make all the difference.

Acrylic, Cellulose and Twin-pack paints are not called synthetics.

So try polishing a Linseed oil based paint or single component Polyurethane paint by hand or mechanically and see what you get, these are all synthetic skin forming paints that cannot be polished the same as car finishes.

Stephen.

[stephen.hull]

Have you tried to paint a furniture van, bus or coach using a brush in a modern oil paint? If you have you'd know what I mean with regard to paint not flowing out properly. spraying can produce a different result but try brushing then come back and say they flow out properly.

Stephen