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Painting dry wood... over oil?

Posted by karinl (My Page) on
Tue, Dec 22, 09 at 13:36

I have stripped a few wood things... a lamp, some mouldings, some furniture... and one outcome is that the wood becomes incredibly dry. If my desired end result is a wood finish, I usually go with oil (often just sewing machine oil as once recommended by someone).

But if I want to paint the thing, I have two concerns about painting over such dry wood. One is that the wood might split eventually, and the other is that the wood might soak up the colour more aggressively, making future stripping more difficult (in case I change my mind or a future owner prefers a wood finish).

How should I treat super dry wood prior to painting to ensure the best for the wood and for future ease of paint removal?

Also, I guess it is an associated question to ask about staining, whether a gel stain conditions the wood at all, or is it just a superficial finish?

KarinL


Follow-Up Postings:

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RE: Painting dry wood... over oil?

Feeding thirsty, dry wood and restoring essential oils is a bunch of who-ha that purveyors of various snake oil products like to pitch. Wood will absorb or desorb moisture in reaction to its surroundings until it reaches EMC (equilibrium moisture content), a point at which it is neither absorbing or losing moisture.

The first thing to do is to ditch the sewing machine oil.

If you think you will want to strip it again in the future, I recommend a coat or two of dewaxed shellac. It will seal in just about any contamination, it will stick to anything and anything will stick to it. It will make stripping out paint much easier as it will seal the pores.

As to gel stain, it is designed so it does not penetrate much. As far as "conditioning," I am not sure what you mean, but I suspect it's more who-ha. Stains typically have a lot of thinner, a fair amount of color in either pigment or dye (or both), and if it contains pigment, just enough binder (curing oil, varnish, lacquer or water-based finish) to hold the pigment in place until it's top coated.


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RE: Painting dry wood... over oil?

If you want to paint it, apply a coat of alkyd oil primer like an enamel undercoater. Sand with 220 grit and prime again if it still looks cracked or porous. It will then be ready for whatever paint treatment you want. Changes in moisture content lead to cracking, checking and splitting. Finishing all surfaces creates a situation where the moisture content changes at a reduced rate, giving greater stability.
Casey


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RE: Painting dry wood... over oil?

Thank you for this input. Here are some photos of the lamp, which is one of the items I am thinking about. Recently stripped (and needing one more session, I realize), this wood is so dry that my fingers itch to oil it, like the urge to water a drought-stricken plant. But I suppose the cumulative message of the posts above is that if the wood isn't split yet, then its apparent deficit is a figment of my imagination... and that it might split if I do start oiling it, I suppose.

The reason I mentioned the sewing machine oil... a few years ago I was having a chair re-upholstered and refinishing the wood myself to reduce the cost. The upholsterer suggested the sewing machine oil, which I did - it made for a beautiful matte finish that is still standing up well. The oil is colourless, odorless, and leaves no residue. My thought here was that it might be possible, with such a light oil, to oil a bit before painting... because the stripped wood hasn't left a colour that I like enough to keep.

Anyway, perhaps the pictures will help to clarify why I have this urge to oil rather than just paint.

Thanks for the assistance,

KarinL

Photobucket
Photobucket


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RE: Painting dry wood... over oil?

Just how do you know it's "dry?" Surface roughness? Visual appearance? Neither is a good indication of moisture content.

It appears that there is a bit of residual pigment in the pores. This may or may not come out with additional stripping and/or sanding.

My guess is sewing machine oil is a non-detergent light-weight petroleum distillate, similar to mineral oil. This is fine for cutting boards, but is a non-drying oil. So subsequent attempts to apply a curing finish (paint, varnish, etc.) might be troublesome.

I'd be inclined to sand, prime and paint the piece in the photos.


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RE: Painting dry wood... over oil?

Thank you, Bob's nephew. The words "non-drying oil" seemed to creak open a door in my brain and so I went hunting for info, and clarified both drying and non-drying oils in my mind for the first time - I had just never quite GOTTEN tung oil, for example. I also did some searches on mineral and sewing machine oil and realized just how little I knew. Probably still the case, but I feel a little more informed, and I think I get now why paint wouldn't stick to it.

So why do I think it's dry? Upon reflection, I think I believe the wood to be dry because it is light in colour, but perhaps more because it looks as if it would soak up oil quite readily if I oiled it. It looks thirsty, therefore I assume it's dry. I guess I am anthropomorphizing it! Or put another way, succumbing to "who-ha".

And yes, sanding is on the agenda since I used one of those stupid strippers that requires water clean up. That seems to have roughed up the surface a bit.

Thanks again!

Karin


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RE: Painting dry wood... over oil?

Water will raise the grain (make the surface fuzzy). The wood you have looks like poplar that can be a lot lighter in color in raw form. I would call it "light oatmeal," but names don't mean much. (It can also have green sapwood that will age to a light-to-medium brown). Poplar is a geat paint-grade wood. (The Mona Lisa is painted on poplar.)

In the right hands, it is a great pretender. If I had a nickle for every piece of poplar sold as "walnut" or "cherry," I'd be rich. But for the novice it can be a hard wood to color well as it tends to blotch.

Here is a link that might be useful: info about poplar


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RE: Painting dry wood... over oil?

Good questions and good advice. The only thing that I would add is that the color of the stripped wood is not nearly the color of the same wood when finished. You can get a better idea of the color if you wet the wood with a rag. Then you may decide that you like the color or would like to alter it with a stain rather than paint (and/or glaze).


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RE: Painting dry wood... over oil?

Typically, you can "wet" the wood with naphtha or mineral spirits to get a preview of an oil-based finish (varnish, or oil-varnish blend).

The pigment that remains in the pores of this piece, in its current state, will not be all that pretty.

It's also a good idea to trial a complete finish schedule on a piece of scrap of the same species as the project prior to starting it. It saves a lot of surprises.


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RE: Painting dry wood... over oil?

Wow, who knew that the wood sold as "poplar" is really tulip tree? Silly me, I thought it would be, well, poplar.

We have used poplar trim a lot and while we know it is intended for paint we've left a lot of it unfinished - for going on 17 years! - and it still looks pretty good. I also just used some on a wall panelling project and got some that has some cool black streaks in it, which I am probably going to leave unfinished or clear coated. I've noted the green pieces, and we've mostly avoided buying those, so I'm interested to learn that they will brown up.

This lamp (an old or antique piece) had a dreadful dark glaze of some sort on it that had partially crystalized - I think I bought it partly just to relieve the poor thing of that finish! But I was disappointed that the wood retains the worst of the pigments in the finish, negating any clear coat options, and have decided it is the rare piece where I will be able to bring myself to paint it.

And I guess I'll just suppress the urge to oil it first :-)

Thanks again and happy new year,

KarinL


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