Full Chisel Blog

January 10, 2010

Using Linseed Oil

Filed under: Finishing,Historical Material,Of Interest,Techniques,Uncategorized — Stephen Shepherd @ 11:29 am

 

The only wood finish older than linseed oil is probably animal grease rubbed on wooden objects.  This stuff, linseed oil has been around for centuries and a ubiquitous wood finish in the nineteenth century.  It could be easily purchased even on the frontier and it was also easy to grow, although tough on the soil and produces stalks for making flax or linen yarn and cloth and with little equipment the seeds crushed and pressed to produce the oil.

In the raw form it takes months to dry and it has been known for many centuries that it could be made to dry faster by adding certain mineral substances or heating to a boil would improve its drying characteristics and allow the ‘boiled’ linseed oil to dry in about 24 hours.

The boiled linseed oil we get today is chemically boiled as opposed to ‘kettle boiled’ but the results are the same, it dries much faster than raw linseed oil.  Raw linseed oil can be exposed to sunlight and it will thicken and begin to polymerize (dry).  The same can be done with boiled linseed oil and it produces what is called stand or sun thickened oil.  Added to regular boiled linseed oil these cause the oil to flow better and dry faster.

I rarely use linseed oil straight unless I want a real fat oil, I generally thin it 50% with spirits of turpentine to make it a lean oil, to help in penetration and to add the subtle characteristics that it contributes to the final finish structure as well as to cause it to dry faster.  I do not use other thinners like mineral spirits because it is a twentieth century invention, is dangerous, stinks, etc.

The trick in achieving a decent oil finish is to follow a few simple instructions.  Put on an adequate coat of linseed oil to all surfaces, applying more oil where it absorbs in and rubbing it with your hand or a cloth in a way to cause friction, hence heat which will help drive in the oil and helps in drying.  Then wait 10 minutes or so and wipe off all excess.  This is very important that all excess is removed from all surfaces.  The surface may be uneven, but don’t worry, this is just the first coat.  Just make sure the surface doesn’t have a large amount of oil, as it will skin over and remain sticky.

Then depending upon the temperature and humidity, it will dry in 24 hours, longer at lower temperatures and higher humidity.  An increase of 10° (F) in temperature will half the drying time and air circulation also helps in the setting or drying.  After the surface is completely dry the surface can be scraped or sanded smooth, the dust removed and a second coat is added following the above directions.  The second coat is usually a fatter oil (60% or more oil and 40% or less turpentine) which will adhere better following the old adage fat over lean.

Here is another traditional idiom:

One coat a day for a week, one coat a week for a month and one coat of month for a year.

Linseed oil as it dries forms a linoxyn film and with repeated application can produce a ‘film’ finish.  A linoxyn film has no known solvents and must mechanically wear off.  A few coats of linseed oil will produce a satin finish; repeated applications will improve the sheen with every properly applied finish.

It is a good idea to scrape or sand the dry finish between all coats except the final.  If there is any roughness on the final finish then wiping off with a coarse linen cloth (there fibers are sharp) will produce a tacitly smooth finish.

To renew a worn oil finish, the surface should be washed with soap (not detergent) and dried completely, then the surface is lightly sanded, the dust removed and additional coat(s) applied as needed, again following the above directions.

It is an easy to use traditional finish that is made from natural renewable materials, you can grow and make your own oil if you want, or you can buy a gallon and start finishing with this excellent and proven finish.  Linseed oil can also be a medium for stains and a solvent for some dyes; mixing the oil with dry powdered pigments or artists oil colors or with alkanet root for a fine wood dye.

Linseed oil is an excellent first coating that enhances the look of the wood by ‘popping’ the grain and can be over-coated with shellac or varnish and is also a main ingredient in oil varnishes.  It can also be used as an isolating coat between coats of shellac.

And as always dispose of oily rags properly.  They should be spread out flat in a dry airy place, preferably outdoors, stored in an air tight container, burned immediately or placed in water to prevent them from catching on fire and burning down your shop and house.  A wad of oily rags will catch on fire by spontaneous combustion, so be careful.

Stephen

16 Comments »

  1. I share you enthusiasm for linseed oil, and this last year have been using it in some paints and in it’s pure raw form. I have a deep fat fryer and fry my spoons, bowls and plates, turned on a pole lathe, in it. Yes it does take months to dry, but is a fantastic finish.
    My question is how long do you boil it for? so that it dries faster. How long do you sun bleach it for, and is that in an open tray or in glass or plastic containers?

    On another note, do you know if linseed was used for waterproofing wooden cups and drinking vessels. Up to now I have only used raw melted beeswax soaked into hot wood. This is a fantastic liquid proofer for any cold drinks and alcohol but obviously not for hot liquids. Do you know if linseed can stand up to repeated alcohol (spirit) use and hot coffee etc? I am still in the middle of my testing and may not find my own answers for another year or so.

    All the best Sean

    Comment by Sean Hellman — January 10, 2010 @ 3:22 pm

  2. I have heard the same idiom, but followed with “Once a year for the rest of your life.”

    Ken

    Comment by Ken Pollard — January 10, 2010 @ 4:23 pm

  3. Sean,

    You only need to heat the oil up to over 250 degrees (F) then let it cool, it doesn’t need to boil for long just come to a boil. For drinking vessels I use walnut oil, which takes time to dry but the wood can be stoved to shorten the drying process. It can take a couple of months for the oil to thicken, the same for bleaching. You can use an open tray and let it form a skin. My stand oil has been standing for over a year and is quite thick but acts as a drier when added to linseed oil to make it dry faster.

    I am going to do some experiments on a couple of other techniques which I will post after I get the results.

    Ken,

    I will make sure I add that to the list.

    Stephen

    Comment by Stephen Shepherd — January 11, 2010 @ 7:46 am

  4. HI stephen

    What would be a good approach to finish a white pine piece with Boiled linseed oil but without the blotching. A primer coat of shellac maybe? thinned Hide glue?

    Thanks

    Martin

    Comment by Martin — January 12, 2010 @ 10:32 am

  5. This is a very interesting topic, and I’m curious what is good source material to read up on it? What sources are good for documenting the finish types?

    I share a bit of the passion for old ways of working, and have been recently putting theory into practice and starting down the path of hand tool wood working.

    badger

    Comment by Badger — January 12, 2010 @ 10:46 am

  6. I like Solvent Free Paints Linseed Oil. No metallic driers added. If i was going to use linseed oil in food contact surfaces I would go with theirs.

    Comment by James Ogle — January 12, 2010 @ 10:49 am

  7. Linseed oil is also a superior seaoning oil for ironware- apply while very warm. Blackens nicley and gives a very good protective finish

    Comment by Mr. Westover — January 12, 2010 @ 1:23 pm

  8. Martin,

    Welcome and a thin coat of heavily thinned shellac or hide glue size (10% glue, 90% water) will seal or size the piece and reduce splotching.

    badger,

    Welcome to you too, the best information will be published later this year and it will cover this and many other 19th century furniture and woodwork finishes.

    James,

    Welcome as well, I haven’t heard of those folks but I will look them up.

    Mr. Westover,

    You should use raw linseed oil, no metallic driers and at those temperatures it will ‘kettle boil’ the raw linseed oil instantly.

    Stephen

    Comment by Stephen Shepherd — January 12, 2010 @ 3:21 pm

  9. Thank you Stephen, this is realy good info!

    Comment by David Gendron — January 13, 2010 @ 12:36 am

  10. Looking forward to reading the book.

    As for finish, I read on Dan’s Blog about Tried and True, which looks good. I bought a quart of it today to try out on a simple pine box I made over the holidays.

    Here is his post on it, that I really liked:
    http://dans-woodshop.blogspot.com/2008/06/tried-true.html

    badger

    Comment by Badger — January 13, 2010 @ 7:49 pm

  11. Gainsborough Products makes a linoxyn remover. Product #PC-211, Linoxyn Remover.

    Comment by Metalworker Mike — January 14, 2010 @ 4:33 am

  12. Thanks for sharing this! I love the look of my current project after a first handful of coats of boiled linseed oil, first time I’ve used it. However, I need a little more protection. Do you have any suggestions that avoid the plastic look of wipe-on poly and the like? Something that doesn’t lose mess with the beautiful depth the BLO brought out in the wood? Thanks!

    Comment by fitzhugh — September 8, 2011 @ 4:51 pm

  13. Great info. I’m trying to duplicate the alkanet and linseed oil wood stain used by english gunmakers. Should I use raw, chemically boiled, or heat boiled? I do intend to thin with Turp before applications. (fat after thin, etc.) Also, for infusion amounts, four TBSP of alkanet powder per cup of oil is what I’ve been able to find. Does this sound about right?
    Thanks
    Ken

    Comment by KenMar — March 23, 2013 @ 6:19 pm

  14. Ken,
    You can use any of the oils, raw taking a bit longer to dry. The proportions sounds good, let it soak for a couple of days to pull the dye materials from the alkanet root.

    Stephen

    Comment by Stephen Shepherd — March 24, 2013 @ 6:30 am

  15. Thanks,
    I’ll let you know how it turns out.
    Ken

    Comment by KenMar — March 24, 2013 @ 10:21 am

  16. its been used inside of 4130 aircraft tubing for many years, to protect against rusting from the inside.

    Comment by grant — September 26, 2013 @ 4:36 am

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