Mixing linseed oil with oil based stain?

[Brinkman]

So, I have started to do some test painting for my current build of a 15th century cog. It is in pear wood and I would like a Stockholm tar look.

 

I have a tar coloured oil based wash but it is too dark for my liking. I tried mixing it with turpentine and did not like the consistency at all.

 

But when mixing it 50/50 with linseed oil I got something that I really liked. But I was told by some hardware store staff not to do it.

 

Is there some reason by I should not mix these two oil based products?

[druxey]

They should be compatible. However, the drying (polymerization) time may be quite lengthy. Try on scrap first!

[Roger Pellett]

I’m Assuming that your Tar Colored Wash is what Americans would call an “oil based wood stain”.  This is nothing more than artist oil colors mixed in linseed oil so diluting the stain with more linseed oil should work fine.  I agree with Druxey that stains don’t cure rapidly as they are intended to be top coated with varnish.  There is a product called “Japan Dryer” that when added to linseed oil based coatings speeds up curing.  It should be available wherever you buy paints.

 

Roger

 

[Bob Cleek]

I don't know if it is the same in Sweden, but in the U.S., "raw linseed oil" is as it says, linseed oil with nothing in it. What is also sold as "boiled linseed oil" isn't boiled at all, but is rather linseed oil with some Japan dryer added to speed the oil's polymerization (drying.) Additionally, "food grade" (meaning "you can eat it") linseed oil and "flax seed oil" often sold in health food stores are essentially the same product, although sometimes produced by slightly different processes. Food grade flax seed oil is also produced according to safe food-processing protocols while non-"food grade" products are not and may be unsafe to eat. 

[Brinkman]

Thank you for the quick answers! Then I will proceed with test samples of different mixes.

[Roger Pellett]

And of course, you can make up your own custom color by mixing artist oils, the kind sold in tubes, with linseed oil.

Edited November 8, 2023 by Roger Pellett

[Dr PR]

True Oil is a "purified" linseed oil that is used on gun stocks. It has no color and dries into a hard clear finish that does not yellow with time. I think it may also have some other oil additives. I have used it and the finish is as good today as when I applied it over 60 years ago.

 

It might be a good oil to mix with oil paints. I haven't tried it.

[Bob Cleek]

3 hours ago, Dr PR said:

True Oil is a "purified" linseed oil that is used on gun stocks. It has no color and dries into a hard clear finish that does not yellow with time. I think it may also have some other oil additives. I have used it and the finish is as good today as when I applied it over 60 years ago.

 

It might be a good oil to mix with oil paints. I haven't tried it.

Yes, Birchwood-Casey Tru-Oil should work fine mixed with oil paints, although it's a quite expensive way to make paint. Tru-Oil is made for the shooting sports market as one of a large range of such niche market products marketed by Birchwood-Casey. (Many modelers may be familiar with Birchwood-Caseys "Brass Black" metal finishing product modelers use for blackening brass model parts.) Tru-Oil is simply linseed oil cut with a solvent with a little bit of a siccative added, the exact formulation of which is undisclosed on their MSDS because they deem it "proprietary." A siccative is an oil-based drying agent that accelerates (catalyzes) the hardening of drying oils.  These catalysts were traditionally hydrocarbon carboxylate chelates of lead, but due to lead's toxicity, cobalt and other elements, such as zirconium, zinc, calcium, and iron, have replaced the lead in more popular products. Most driers are colorless but cobalt driers are a deep blue purple color and iron driers are reddish orange. These colored driers are therefore compatible only with certain darker pigmented paints where their color will be unseen. 

 

Separate drying additives for paints became necessary as zinc oxide-based paints were developed as an alternative to the lead oxide paints ("white lead") that had been previously used. Zinc oxide paints were developed in parallel with the introduction of "oil soluble driers" or "terebines" around 1885. These were lead and manganese soaps of linseed fatty acids or resin, also termed linoleates or resinates. Terebines had poor shelf life in mixed paints, as they auto oxidized and lost their effectiveness. As a result, early factory-mixed paints, unless fresh, were a poor substitute for fresh paint mixed by a painter on site from raw ingredients. This situation lasted until the late 1940s; by then further drier developments had superseded the terebines. In 1925, stable naphthenate driers were developed in Germany and commercialized in the US in the early 1930s, in parallel with the development of durable and fast-drying alkyd resin enamels. In the 1950s, metallo-organics based on synthetic acids were introduced as driers.

 

Japan drier is a common lay term and generic product name for any oil drying agent that can be mixed with drying oils such as boiled or raw linseed oil and alkyd resin paints to speed up "drying". The name refers to "japanning", a term for the use of drying oils as an imitation or substitution for urushiol-based Japanese lacquer. 

 

(Full disclosure: I didn't know all of the above chemistry off the top of my head. I looked it up.  )

 

The question whether Tru-Oil can be colored with artists' oil paint is a good one that is becoming increasingly important to many "thrifty" modelers. While there is a tremendous range of quality modeling paint colors available to modelers today, they are extremely expensive in terms of the amount of paint we get for our money. To be sure, most can afford six or eight dollars for a one-ounce bottle of "store bought" paint, but when the number of bottles on our paint shelf start to mount up and however many are found to have dried up since we last opened them, the savings, flexibility, and convenience of mixing an infinite range of paint colors and gloss levels from readily-available and substantially less costly components without the inconvenience of sourcing them from the internet or searching in a "brick and mortar" hobby store you hope has what you are looking for, starts to become a lot more attractive. Mixing your own model paint can certainly can be done using Tru-Oil as a base, but Tru-Oil is fairly expensive for what it is at around US$35.00 a quart. However, even considering the additional cost of several bucks for a tube of artists' oil paint, it's a bargain compared to the equivalent quart of seven buck an ounce hobby paint totaling US $224 ! Now, if you shop around, both boiled linseed oil and gum turpentine each cost about a US $10.00 a quart, so a quart of "half and half" mixed is going to run about US $10.00 from the big chain hardware stores, which makes Tru-Oil will cost you about three and a half times what its "homebrewed" equivalent will. By using boiled linseed oil and turpentine to make your own modeling paint, exclusive of the relatively negligible expense of the artists' oil paint which goes a long, long way, and other conditional additives that are used in very small amounts, if at all, you've avoided paying almost twenty-two and a half times the cost of commercially premixed model paint! Also, Tru-Oil cannot be shipped to or sold in California, USA, presumably due to California's restrictions on VOC content. (It may also be unobtainable in the E.U., given their often more stringent environmental regulations.) If one can't get Tru-Oil in their area, or simply wants to save some money, boiled linseed oil (which contains driers as packaged) thinned with natural gum turpentine, or raw linseed oil, natural gum turpentine and a dash of Japan drier "to taste," should perform as well at a huge savings. I've long used boiled linseed oil and gum turpentine mixed 50-50 as an "all purpose" furniture and rifle stock finish as well as a furniture finish "restorer" with results comparable to what Dr PR describes from Tru-Oil. Wiping it on and into scratched surfaces such as varnished kitchen cabinets, baseboards, stair bannisters, and case goods, etc. will usually cover the scratches well. (Used just like "wipe-on poly.") I routinely keep linseed oil and turpentine in half-gallon or at least quart quantities in my shop paint locker for mixing all sorts of painter's concoctions. 

 

Quality artists' oil paints (look for finely ground pigment in high concentrations) packaged in tubes can be mixed with boiled linseed oil (or raw linseed oil with a suitable amount of drier) and thinned with turpentine for use as excellent model paint for brushing, spraying, or airbrushing. Raw linseed oil (no driers) and turpentine with a suitable small amount of artists' oil paint can also be used as a stain. If the resulting dried finish's level of gloss is too high, the gloss of the dried finish can be knocked down from high all the way to flat matte by hand-rubbing with rottenstone and pumice, or Scotch-brite abrasive pads made for this purpose, or by mixing into the paint a "flattening agent" which is sold in small, over-priced quantities in art supply stores and in larger, much less expensive, quantities in paint stores. "Flattening agent" is generally just finely ground "whiting" (which is calcium carbonate powder, AKA "chalk" or agricultural lime.) sold in a suspension of solvent to expedite mixing it into paint or otherwise sold as a "bagged" powder like baking flour. Follow the instructions on the container. (Note that if the flattening agent is sold mixed in a solvent, the type of solvent has to match the type of paint. Alkyd enamels take one type, polyurethanes take another type, and so on.) A bag of "painter's whiting" is always good to have on hand for many uses including mixing up your own old-fashioned glazier's putty (and wooden boat plank seam stopping) which is why it is sometimes sold as "glazier's whiting." (When used as putty, it is mixed with raw linseed oil alone so it won't harden as quickly.)  If an old-timer tells you that adding gasoline to your paint will work as a flattening agent, don't risk your life finding out. It used to be true. In the '50's and '60's we kids would use it on our plastic car models and it worked great, but that was then. Now, the lead derivative once used to make high-octane "ethyl" or "leaded" gasoline which were responsible for the flattening effect when we'd mix gasoline in our model paint or apply it directly to styrene plastic has been outlawed for public health reasons. (Back then, a kid's life was an adventure! We'd drink out of garden hoses, ride bikes without helmets, eat unpackaged Halloween candy, and all sorts of other really dangerous stuff. If your mother said you might put somebody's eye out doing it, you just knew it had to be fun. No wonder the younger generation today are such a bunch of wusses!  ) 

 

There are lots of formulas online for mixing your own clear varnish that basically the same as the paint formula above, save for the addition of resins or differing oils, but for many applications an epoxy or urethane clear coating is to be much preferred over a low-tech traditional varnish and for any application where the finish will be exposed to direct sunlight, UV inhibitors are a must. At that point you get into more complex modern-day coatings technology and the traditional "DIY paint-making process" becomes more trouble, if not more dangerous, than it's worth and you are better off buying it mixed in the can from the paint store.

Edited November 8, 2023 by Bob Cleek

[Roger Pellett]

Bob,  As our resident paint chemist, what about Japan Colors?

 

Roger

[druxey]

I think Bob said and covered it all!