Scalecoat I, thinners, and temperature

[mmagliaro]

I just painted my NP radial roof boxcar.
I used Scalecoat I paint, from brand new bottles.  The paint stirred up and looked beautiful.

But... I had a lot of trouble with airbrush clogging and some clumping in the paint cup that seemed to start
the moment I added thinner to the paint.   
I was using a generic "Paint Thinner" (made by Sunnyside, from the hardware store).
I have never had any trouble thinning and painting Scalecoat with this before (same can, too!)

The paint seemed to almost start forming a "gel" in it when the thinner went in, which I have never seen.
If I added more thinner, it would smooth out and I could eventually make it work.

So, my questions:
1. It's really hot here in Oregon right now, in the high 90s, but my garage is NOT that hot, maybe 80.
I can't remember if I've ever painted in weather that hot before.  Can that cause this clumping?

2. Is that "paint thinner" a lousy thinner that I shouldn't use?  I used to use the geniune Scalecoat thinner,
but it's pricey and years ago I stopped using it in favor of hardware store thinners and never had any trouble.

So....
What would be better?
Mineral Spirits?
Lacquer Thinner?
Automotive paint thinners?

This topic has unfortunately raged for years if you surf the web and read up on it.   I'm looking for something
commercially available NOW, in 2015, that is a good formula for thinning Scalecoat 1.

Thanks.

(BTW... in spite of my troubles, I did get the paint to thin out and spray smoothly and the car looks really nice
  )

[Doug G.]

It's been a while since I've had any Scalecoat but isn't it kind of like Floquil in that it is, at least partially, a lacquer type paint? I know lacquer thinner has always worked for me as a substitute for Diosol. I also know Floquil changed their formulation quite a few years ago and the paint smells kind of like a mixture of lacquer and oil enamel. Lacquer thinner still works to thin it, however.

I just think mineral spirits (isn't that what the Sunnyside stuff is?) may not be quite correct for Scalecoat.

BTW, Minuteman Models has acquired Scalecoat paints so that's good news.

Doug

[C855B]

I thought Scalecoat was acetone-based. @peteski knows something about this.

EDIT: Never mind.

[Doug G.]

Then I forgot to address the temperature issue. It certainly can have an effect on paint but I think it is more during the painting process rather than during mixing/thinning. How's the humidity? That will also affect paint/painting.

I think it's Tru-Color that's acetone-based.

Doug

[C855B]

Yeah, you're right. Memory fart. Further poking around I found mentions of lacquer thinner for Scalecoat I (explaining why SC-I is hostile to plastics) and mineral spirits for Scalecoat II. This is third-hand advice - I still have Scalecoat thinners on hand, so I've never sought alternatives.

Max's problem with congealing could easily be from using mineral spirits with a lacquer. I've made that mistake, tho' in non-MRR settings.

[peteski]

AFAIK, There is no acetone in any Scalecoat paints.  I also don't have many Scalecoat I paints.  I mostly use Scalecoat II. I'm not at home right now but IIRC both use either Toluene or Xylene in their thinners plus petroleum distillates (which can mean many different things).  I also think that Scalecoats paints are enamels (which has no direct bearing in how hot their solvent is).  But to me it seems that mineral spirits would not be compatible with any Scalecoat paints.

If the paint curdled up on you, that would seem to indicate some sort of chemical incompatibility between the paint and the thinner.  Assuming that the thinned paint was a smooth fluid and not partially cured.

I prefer using the thinners made specifically for the paints I am using.  I also sometimes use generic lacquer thinner for thinning most organic solvent-based paints.  Just because it says "lacquer thinner" it doesn't make it exclusively for lacquers.   But every brand of lacquer thinner (or even different batches of the same brand) can have different formulations.  I use the SCL brand and in the last 20 years have changed their formulation coupe of times.

So, my recommendation still stands: if you want 100% compatibility, use the paint-specific thinner.  Otherwise try to find the ingredients of the paint's solvent (thinner) and try to fins some generic thinner which has a similar composition.

[sd45elect2000]

I've always had good results with lacquer thinner, The brand you mentioned never failed me. I've never used mineral spirits.

Randy Stahl

[mmagliaro]

You know, it's funny because I keep a little screw-cap jar on my workbench for cleaning and I even have it
labeled "Lacquer thinner" in Sharpie marker, which makes me think that in the past, I was probably using
lacquer thinner and now have a "paint thinner" which is not at all the same stuff.

I also realize that for a while, I've been painting with Floquil, not Scalecoat.
This "paint thinner" has been working fine with Floquil, but maybe it does not work well with Scalecoat.
They are definitely not chemically the same kind of paint.

When Floquil went down and I switched back to Scalecoat, I am not sure that I actually tried thinning it with
this "paint thinner" until now.     Sooooo....  off to buy some lacquer thinner to see if it works better.

BTW, the humidity isn't bad at all, and I tried the thinner in some Scalecoat this morning, when the temps are much
cooler (in the mid 60s) and the congealing still occurs, so it's not an environmental problem.

(and yes, years ago, when I exclusively used Scalecoat, I always used their branded thinner, but I don't happen to have
any right now, and I mistakenly assumed that this "thinner" I've been using would work).

[Sokramiketes]

Yes, the lacquer thinner will fix you right up.  Floquil and Scalecoat II are compatible, not Scalecoat I, as I've swapped thinners between the two before.  The big cans of Scalecoat II thinner were cheaper than Floquil for awhile, and worked great.

[mmagliaro]

Thank you!

The "paint thinner" I happen to have is also "odorless", which made me suspicious that it must be
a weak substitute for the real thing.

So I did some reading on paint thinners and where they really fall in the distillation process.  And found this...

First, "paint thinner" and "mineral spirits" are the same thing.

Second:
"The mineral spirits left after the toluene and xylene are removed is sold as “odorless” mineral spirits. When understood this way, it’s obvious that odorless mineral spirits is a weaker solvent than regular mineral spirits. "

And bearing in mind that Scalecoat I thinner is supposedly xylene and toluene... ahem... that means that
regular paint thinner probably did used to work for me but this odorless variety is devoid of the very
essential elements that probably used to make it work.

I will buy a couple of cans of different stuff, including lacquer thinner, and do some tests.

[Doug G.]

Regular paint thinner or mineral spirits is what you want to use for oil enamels, however. Like Testors Pla or Pactra.

Doug

[mmagliaro]

Regular paint thinner or mineral spirits is what you want to use for oil enamels, however. Like Testors Pla or Pactra.

Doug

YES YES YES!  Doug gets the blue ribbon.  I remember now.  I bought this thinner from a custom paint store
where I had them mix me some NP Loewy Dark Green based on an NPRHA color drift card.  And they mixed
it for me in solvent-based enamel.   Although I've gotten mixed up on the history of this,
I remember that for sure because it was the only type of solvent-based paint they could custom-mix
for me, and I asked them about spraying it through an airbrush.   

That explains why I have this can of thinner.

[peteski]

There is a lot of misinformation and incorrect paint and solvent nomenclature being passed around in the modeling circles. Things like equating acrylic "paint" or enamel to mean that uses water based solvent/thinner/vehicle.  There are plenty of acrylic-based  enamels and lacquers which use organic solvents.

Plus the lack of transparency from the paint manufacturers adds to the confusion.  The labels on the paint or thinner containers are usually very vague about the contents.  This goes both for the specialty model paints and general purpose paints from the hardware store.

I'm no chemist or paint expert but I have educated myself to better understand paint chemistry.  Wikipedia among other sources is your friend.  https://en.wikipedia.org/wiki/Paint Plus the years of experience in using paints and my usual anal nature helped too. 

The general rule that seems to apply to thinners is that a "hotter" thinners can be used with paints based on "cooler" thinners but not the other way around.  The "hotter" and "cooler" thing is another generalization, but it seems to work how we use and describe hobby paints.  BUt a word of warning - while the hotter thinner will thin the paint, it might change its drying time, and of course if it is hot enough, might affect (soften or craze) the plastic surface being painted.

I have in front of me I have some thinners:

1. Floquil thinner and solvent for use with railroad colors (yes, that is the full name).  It is for the Rev I (plastic compatible) paints Floquil introduced in the early 80s.  Not the Dio-Sol used with the original formula (hot) Floquil paints.  The label only states "contains petroleum distillates", which is really vague (but is is often used by paint manufacturers to describe contents of paints or thinners).

2. Scalecoat (I) thinner.  Label states TOULOL (aka. Toluene) and XYLOL (aka. Xylene).  Again vague, but not as vagule as Floquil. Still., there could be other ingredients - not listed.

2. Scalecoat II thinner. Label states XYLOL and PETROEUM DISTILLATES.  Again, very vague.

Searching the Web for MSDS for each of the above could yield more detailed listing of the contents.  Here is one informative thread I found:
http://www.modelrailroadforums.com/forum/showthread.php?26755-What-Is-A-Good-Substitute-For-Dio-Sol

[mmagliaro]

Thanks, Peteski.  I've been doing some web reading on this myself.
I hate being kept in the dark by manufacturer labels.

Here's a great article:
http://news.thefinishingstore.com/index.php/understanding-solvents-part-i/

They basically go through the entire hierarchy of petroleum solvents, explaining what they are, which are
"hotter" than others and what you are likely to find in a can when you buy it at a consumer store.

I just came back from the paint store (a real paint store, not a consumer home supply place staffed by, well...)
This is the same place that mixed my NP green enamel.  It is a pleasure to talk to guys who
do one thing and do it well.  Whew.

Anyway, I described the problem and he immediately said, "Yep, the thinner just isn't 'hot' enough.
I showed him what I had been using and he agreed that lacquer thinner or Xylene would work much better.

Incidentally, you can indeed still buy xylene and toluene.  He had them both, and I could have mixed up
my own "Scalecoat I Thinner" (assuming that those are the major ingredients).

I'll try the lacquer thinner and xylene tonight and see how they act.  I can also see what they do when I brush
them onto some scraps of plastic.  (It would be good to know if they attack plastics badly).  Although even
with the old true "Scalecoat I" thinner, I never had any trouble spraying plastic.  I think the trick is just to
not blast it with a heavy coat right off (which I never do anyway). 

I love the smell of solvent based paints in the air.  It smells like... victory.

[peteski]

I'll try the lacquer thinner and xylene tonight and see how they act.  I can also see what they do when I brush
them onto some scraps of plastic.  (It would be good to know if they attack plastics badly).  Although even
with the old true "Scalecoat I" thinner, I never had any trouble spraying plastic.  I think the trick is just to
not blast it with a heavy coat right off (which I never do anyway). 

Acetone, toluene and xylene will affect polystyrene, ABS, and acrylic plastics. But how much depends on the specific plastic's formula (for example, not all polystyrene are the same - they have various additives). It varies from model to model and from manufacturer to manufacturer.  Some of the above mentioned solvents will melt the surface smooth, others will craze it. Humidity will also affect the results. When solvents evaporate they cool the surface they are evaporating from.  If it cools enough for the water vapor in the air to condense, the surface will "blush".

Also keep in mind that those hot solvents are present in many plastic-compatible paints.  But the amount of those solvents in  proportion of other ingredients on the paint results with the paint being safe to use on plastics.