# Testing for oil paint



## JubJub (Mar 13, 2011)

So this is a pretty basic question and usually I have no problem figuring it out, but I've come across some trim that is questioning my usual testing technique. I'm trying to figure out if there is oil or latex on the trim. It looks like it could be either (if that's even possible). I've taken a clean rag and rubbed "goof off" on it and I've also used denatured alcohol. Both have taken some of the paint off (color on the rag) and have burnished the surface slightly, but neither has made the surface tack up like latex usually does. I've had trouble in the past where I've tested some trim, the "goof off" took it down to what was underneath the topcoat but didn't tack up, and it ended up being oil based (i figured this was caused by the topcoat being 20 years old and oxidizing like crazy over that time period). Obviously, the latex didn't bond well. I'm hesitant to follow through with my estimate until I can figure out for sure what it is. 9 times out of 10 the results are pretty precise and easy to figure out. This is not one of those times. Anyone had this experience? Does my explanation make any sense? Thanks!

p.s. By the way, this is an interior job on a 20 year old house. It's been painted only twice. The homeowner has no idea what was used and no leftover paint.


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## billy the kid (Jan 22, 2011)

i sorta just went through this issue on a church product and live and learn my new rule is when in doubt assume its oil....


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## jack pauhl (Nov 10, 2008)

Sounds like oil. Any paint chips to snap in half? Did you try lighting a piece? Squeak test help any?


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## JoseyWales (Jan 8, 2011)

I believe acetone is another tester...It will remove latex but not oil...


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## expertpainter (Nov 13, 2010)

*When you're not sure if you are painting over oil or latex.*

Here at Toronto painting contractors we found that when it wasn't sure of what we were going to paint over we had two options then. The one was we would always prime down with oil primer or we were thoroughly sand and de-glaze completely the surface in question leaving a matte finish. We then proceeded to apply a high quality latex primer.


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## timhag (Sep 30, 2007)

DYI'er ! HIT THE ROAD JACK!


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## JubJub (Mar 13, 2011)

Jack,

The surface is pretty sound so there aren't any chips to snap or light. What is the squeak test? Never heard of that. I was hoping to avoid oil priming, but it looks like that might be the answer. The customer may have a heart attack with that added cost. It's already estimated at over $8000 for the entire interior! I did apply some BM Regal semigloss to a couple of small areas on the trim to see if it would bond. If not I can always sand it off easily. Thanks for the input, guys!

timhag,

Been painting for 10 years. Constantly learning new things. That's how you get better. And it's DIY.


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## Roadog (Apr 18, 2007)

On some projects.....dont assume its either oil or latex. Especially in a church. They used distemper, casein, lime paint, mineral silicate, and sometimes just tinted the plaster. I just use denatured....it will pull color off latex but not oil. Sometimes oil is chalking you might get a little but after some experience you can tell. Goof off has toluene and I'm not sure that it wont loosen everything. 

Doing a test tomorrow. Church wanted a bid, they said its the finish from 100 years ago. Days later went back and first time I ever saw plaster walls and ceiling 100 years old with not one crack. Then noticed up close I could see the "grit" of the sand. Then noticed its tinted all the way through. True craftsmanship.... So now I am looking into it more, one reason is the average paint company will give an estimate and proceed with primer and paint, (will start peeling in 10 years) killing this plaster/cement? When really it sounds like mineral silicate would be the best option and never have to paint again for another 100 years.

SW has a water base bonding primer to go on oil. Tried it....paints nice, sands good and is on like a rock. Good stuff. Cost more though than oil but well worth it.


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## Wolfgang (Nov 16, 2008)

Some things to look for:

Age of house a/o trim if it's remodeled
Different layers of paint
Razor test it.....take a new single edge and pull it towards you with just enough pressure to break the surface.
Put some thinner on a rag and hold it on the piece for a minute...oil will usually start to form a bubble.


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## propainterJ (Jan 31, 2011)

Take a piece of sandpaper to it.

Does it roll up like latex or powder?

If all else fails put a little of your finish on a small piece and look the next day.

Jesus it aint brain surgery.


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## Bender (Aug 10, 2008)

JoseyWales said:


> I believe acetone is another tester...It will remove latex but not oil...


Josey, acetone is way way way to hot. You might be thinking of denatured alcohol?

Another test is look in the closets or pantry- anywhere that doesn't get sunlight. Alkyds will yellow something fierce. I have seen some of the earlier waterbourns do it as well but not as much.


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## sage (Apr 29, 2007)

Bender, that works if its white but what about dark colors?

Wolfgang, thanks for the razor test info., had not heard of that before.

Sage


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## Bender (Aug 10, 2008)

sage said:


> Bender, that works if its white but what about dark colors?
> 
> Wolfgang, thanks for the razor test info., had not heard of that before.
> 
> Sage


Guess I never thought about it that way:icon_redface:
Good point.


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