Why is painting so hard?

[Swede]

For years, I've been envious of projects that have components finely painted. I'm trying to learn how the pros do it, and of course it boils down to experience, and having good spraying gear.

I picked up a nice Paasche air brush, and have been thrilled with the results. For larger items, I'm using a cheap Harbor Freight detail gun that also seems to work well. But the paint (and thinning) seems like voodoo to me.

In the last few years, paint companies have stopped giving thinning recommendations because of environmental concerns. I've got a can of "Ace" oil-based alkyd enamel that I want to thin so I can spray a primed aluminum plate that is 12" X 18". No thinning instructions at all on the can.

I've got Naptha, xylol, toluol, and mineral spirits. I read somewhere that South Bend originally thinned enamels with Naptha, as it gave a more durable surface. This surface will be exposed to oils and such.

Which solvent would work well? Any tips would be much appreciated. TY

 

[steamer]

Wish I could help ya Swede....I don't know squat about paint though........other than Rustoleum works! ;D


Dave

 

[Tin Falcon]

Swede I am trained as a painter trained to follow manufacturers instructions.
So check the manufactuers web site.
If that fails look here The US Army corps of engineers painting manual
http://140.194.76.129/publications/eng-manuals/em1110-2-3400/toc.htm
or USAF painting manual here http://www.robins.af.mil/shared/media/document/AFD-091006-043.pdf
Tin

 

[gmac]

Swede;
A possible starting point;

http://www.fastenal.com/web/products/detail.ex?sku=0160555

Do some homework though - I recall someone telling me that the alkyd enamel thinners simply slow down the setup time allowing the paint more time to lay down flat.

Cheers
Garry

 

[Tin Falcon]

another way to go is look up an msds sheet it may give you the carrier used in the paint. worth a try.
Tin

 

[Troutsqueezer]

There's a lot of info out there on this topic, especially the modeling forums such as RC Universe. For Alkyd enamel, try thinning it to 25% Naptha (or equivalent) and 75% paint. That's what I used on my tractor and it came out well. Experimenting is really the way to go because the usage of paint reducers can be dependent on your specific environment such as temperature, humidity, etc.

I like the Paasche compressor and had one for a number of years. I bought a Harbor Freight one a while back and actually like it better because it only runs when the pressure gets below the set point whereas the Paasche ran constantly. I even had to add my own on/off switch to the Paasche since it was plug in only, with no power switch.

-Trout

 

[Mosey]

I have had success using one of those little viscosity testers that you dip in the paint and watch how long it takes to drain through. This makes Dodo's like me barely able to paint. Of course, it is mandatory for me to always test the set on the newly painted surfaces by touching it with my fingertip, thereby messing up an otherwise good coating.
Painting-challenged Mosey

 

[Swede]

Thanks for some good info. Browsing the web seems to find a dozen different ways to thin, and I wanted to hear it from guys who actually do it.

It's very odd that paint manufacturers are limited in what they can suggest for thinning due to the VOC reduction laws. I know enamels have been thinned for spraying since they've been invented, but these little cans I bought have no thinning information at all on them.

Yes indeed the MSDS should show the main solvent... that's a good place to start.

 

[Ken I]

One problem I've experienced - if you spray parts at room temperature - the evaporation of the solvent causes cooling - can easily get below dew point and cause condensation which will minimise the gloss you may be looking for.

Similarly the paint runs a lot easier (particularly first coats).

My spray painting has improved by working on pre-warmed parts.

2c Ken

 

[rkepler]

Absent manufacturer's instructions I thin with whatever solvent family used in the paint - typically xylene or tolulene. If it's warm I use the slower thinner so the paint doesn't flash off as quickly (painting a couple of days ago I had paint flashing off before I could get the gun away - that's Albuquerque for you). I tend to over thin paint and make multiple passes at half or 1 hour intervals, getting a couple of passes onto most everything.

 

[Stan]

I have painted everything from busses to meter dials and I can tell you that the smaller it is, the harder it is to paint.

If painting with a spray gun, on a large surface, you can start shooting in the air, make a pass and end up shooting in the air. That gives you an even coat and dirt specks, paint lumps etc virtually disappear on a large surface. These same small imperfections stick out like a sore thumb on a small surface. If you are painting small irregular parts, it is almost impossible to turn it around to get complete coverage without getting too much paint on some areas. Multiple light passes are mandatory on small parts but if you are using any of the catalyst activated paints you have time restraints as to when you can recoat.

For the majority of paint work on models, it is hard to beat the good quality rattle cans. Paint quality and color are quite consistent, you don't need an elaborate spray booth and there is no cleanup.

 

[Ken I]

I'll back Stan up on that one - I have a good quality spray gun, airbrush and compressor - but for most small jobs I still use a spray can - its just less hassle.

Ken

 

[Mosey]

I'll back Stan up on that one - I have a good quality spray gun, airbrush and compressor - but for most small jobs I still use a spray can - its just less hassle.

Ken

Yes, and putting them in hot water first, helps get the paint to spray nicely, and using one of those clip-on spray handles also helps.

 

[zeeprogrammer]

This is a very useful thread. Thanks for starting it.

 

[Tin Falcon]

for small parts to need to be able to urn the object either hang it or on a turntable. Light coats many angles of approach.
And if painting light bright colors like yellow or orange use a white base coat. makes a huge difference.
Tin

 

[Swede]

I'm going to shoot the plate today. It was primed with a catalyzed aircraft metal primer, really good stuff, and the priming went excellent. I'm going to try Hunter Green alkyd enamel, thinned with xylene.

Its HOT in Texas, and the humidity is down, so dewpoint won't be a problem, but drying too quickly might be. And I'll snap a couple of pics. Here we go!

 

[Swede]

I set the plate up hanging by a cord, and thinned the paint about 5 to 8% with xylene. It didn't need any more than that, as the heat made the paint free-flowing to begin with.

The plate already has a good strong coat of the 2-part catalyzed primer:

The gun is a harbor freight cheapie that performs better than the price, I think. I've personally had better luck with gravity fed guns like this, with the cups on top.

The first coat... a light one. Seemed to go on well. After this initial coat, I took these pics, then added 3 more coats at intervals of 10 to 15 minutes. Since this is the first coat, the color coverage is not complete, and you can see primer through the paint. Right now, after 4 coats, visually it looks good, nice and even. I'm sold on spray equipment like this. Cleanup is a pain, but the results are worth it, IMO.

I'm planning on unleashing my Paasche air brush on some steam engine cylinders and the like.

TY all for the advice.

 

[Ken I]

Yup - Don't worry too much about the thickness of the first coat - that's when you get runs.

Moseys comment on warming up spray cans before use is a good tip - especially when the weather is cold.

I normally use my hot air gun whilst shaking vigorously - hot water is definately a safer way to do it.

Ken

 

[Antman]

I'm surprised nobody recomended acrylic paint, with its advantages of easy clean-up, water thinning and quick drying time. I haven't used a high gloss acrylic yet, but I understand it's available.
Ant

 

[Stan]

How did you get even cover behind the string that the plate is hanging on? My experience is that even a fine wire will show up as a missed line. Coming at it from a different angle just means that you have more paint everywhere else when you cover the line. By doing multiple thin coats, you get good cover but big differences in paint thickness.