"cooking" raw linseed oil

[Harlan Barnhart]

I'd like some real boiled linseed oil. I can buy raw oil easily enough but I've heard the heating process is tricky. Has anyone done this? If not, why not? Maybe the rest of you have a secret vendor who sells BLO without chemical dryers.

I've also heard of setting raw oil in the sun for extended periods of time to "thicken" it and speed the dry time. Does anyone know about this? I want a finished product I can use around my children and without gloves.

[george wilson]

Why not just buy boiled linseed oil? I made varnish for many years,and I can tell you that it is a tricky and dangerous occupation. There's more to boiled linseed oil than just boiling it. It also has driers added which need to be done by a chemist who knows what he';s doing. Batches of varnish and oils are made up in large ladles of over 55 gallons. Adding driers to a very small about of oil will be tricky,and could leave you with a defective product.

It's also an operation that should ONLY be done out of doors over a flameless hot plate. Believe me,it's an excellent way to burn your house down. NEVER do it indoors.

Sun thickened oil is "stand oil",and it is indeed thick. Used by the old Dutch masters to impart gloss to their paintings.

[Zach Dillinger]

Harlan, you can use raw linseed oil to finish. Just rub in many very thin coats rather than flooding the surface. I do this because BLO gives me a headache, I'm assuming its the chemicals in it, so I use food grade linseed oil. Costs a lot more but at least I can use it without my head hurting.For more info on linseed oil, check out Stephen Shepherd's Full Chisel blog. He has written extensively on the topic. My favorite technique that he wrote about is to use diatomaceous earth (also known as rottenstone) to cook the oil. I do this quite often.Zach

[Cody Cantrell]

I have not tried this but these directions seem easy enough.
http://www.wkfinetools.com/tRestore/finish-wood/kramer1/kramerImprov.asp
Were do you get raw lunseed oil? I have looked all around my neck of the woods bit cant seem to find any.

[Zach Dillinger]

I have not tried this but these directions seem easy enough.http://www.wkfinetools.com/tRestore/finish-wood/kramer1/kramerImprov.asp Were do you get raw lunseed oil? I have looked all around my neck of the woods bit cant seem to find any.Health food stores have food grade, which is what I use.

[Chris Griggs]

If you want plain boiled linseed oil with nothing else in you can always pick up a can of Tried and True (http://www.triedandtruewoodfinish.com/) "Danish Oil". Don't let the name fool you - this is not an oil varnish like watco - it is the simplest finish the company makes. Just moderatly polymerized linseed oil. They also make their "original" which more polymerized and has beeswax in it, as well as an "oil varnish" that I believe uses some type of sap that allows it to build and harden a little. I keep a can of the original around. None of their products have any driers either. This does however mean you need to apply light coats and rub the finish out. As far as end result, I don't necessarily think it looks any different then hardware store BLO, but I like the company and I like what goes in (or doesn't go in) to their products.

[Harlan Barnhart]

Why not just buy boiled linseed oil?
I would like to buy boiled linseed oil WITHOUT the petrochemical dryers. Just raw oil that is "boiled".

Sun thickened oil is "stand oil",and it is indeed thick. Used by the old Dutch masters to impart gloss to their paintings.
What can you tell me about stand oil? Does it noticeably decrease dry time? I have seen BLO thicken from sitting in an open container for an extended period of time, its that similar?

[Harlan Barnhart]

If you want plain boiled linseed oil with nothing else in you can always pick up a can of Tried and True (http://www.triedandtruewoodfinish.com/) "Danish Oil". Don't let the name fool you - this is not an oil varnish like watco - it is the simplest finish the company makes. Just moderatly polymerized linseed oil. They also make their "original" which more polymerized and has beeswax in it, as well as an "oil varnish" that I believe uses some type of sap that allows it to build and harden a little. I keep a can of the original around. None of their products have any driers either. This does however mean you need to apply light coats and rub the finish out. As far as end result, I don't necessarily think it looks any different then hardware store BLO, but I like the company and I like what goes in (or doesn't go in) to their products.
This is good to know. Do you know how they "polymerize" the oil? Is it heated?

[John Lanciani]

Ripped from Tried & True's front page to highlight Chris's answer;

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[Harlan Barnhart]

Harlan, you can use raw linseed oil to finish. Just rub in many very thin coats rather than flooding the surface. I do this because BLO gives me a headache, I'm assuming its the chemicals in it, so I use food grade linseed oil. Costs a lot more but at least I can use it without my head hurting.For more info on linseed oil, check out Stephen Shepherd's Full Chisel blog. He has written extensively on the topic. My favorite technique that he wrote about is to use diatomaceous earth (also known as rottenstone) to cook the oil. I do this quite often.Zach
How does the dry time of raw oil compare to Home Depot BLO? How about raw oil treated with rottenstone? Will it commonly dry in a day? I don't mind a little extra time. My children like to "help" a lot and I don't feel good about them getting commercial BLO on their hands. I'm not that crazy about it on my hands either.

[Chris Griggs]

This is good to know. Do you know how they "polymerize" the oil? Is it heated?

Not sure. But given that they supposedly use and old shaker recipe (or something like that), yes, I believe it is heated. Give em a call or email. I'm sure they can probably tell you a little more about it.

[jamie shard]

Harlan, you might be interested in some of the science/techniques used by painters... this site was a really good read: http://www.tadspurgeon.com/justoil.php?page=justoil . I think some of the methods would work well for woodworking, but I haven't tried it. His goals are similar to a woodworker: a workable, non-yellowing, quick drying oil.

p.s. thanks for you post on the "tansu" thread... so far the "air vent" idea is the one that seems most likely.

[Jim Koepke]

My children like to "help" a lot and I don't feel good about them getting commercial BLO on their hands. I'm not that crazy about it on my hands either.

My hands are always covered with protective gloves when finishing. Costco carried these last time we shopped there. There are just some things in my wood shop, garden and automotive repair duties that shouldn't come in contact with human skin.

jtk

[Harlan Barnhart]

My hands are always covered with protective gloves when finishing. Costco carried these last time we shopped there. There are just some things in my wood shop, garden and automotive repair duties that shouldn't come in contact with human skin.

jtk
Good strategy Jim, even with safe things like shellac. It saves cleaning up your hands.

[george wilson]

Edible linseed oil is not polymerized,and I don't know if it would effectively dry or not. I started using edible linseed oil(flax oil) in my varnish since it is a LOT clearer than the hardware grade oil. BUT, it needs to be polymerized. This is dangerous if you aren't experienced. You MUST work out doors. Use a DEEP container. Oil can get too hot and suddenly foam over the top in an instant,turning into a LARGE ball of fire before you can get the pan off the hot plate.

I AM NOT RECOMMENDING THIS AS IT IS DANGEROUS,TOO,but,I used to saw the top off of an EMPTY,EMPTY propane bottle to get a real tall container. You can blow up the container if any gas is left in it,so I cannot recommend it.

I'd carefully SIMMER the oil and not let it get past simmering for about 20 minutes. It would turn a rich,golden color(from the pale color it was before). Then,the oil was polymerized,and would then be a drying oil. Do not eat it after it is polymerized!!!!

After the oil was golden,I'd add the resins,and carefully simmer it till a drop gotten on the end of a longish stick,would make gossamer cobwebs when touched and pulled away from a bottle. That means the varnish is done. I'm not getting too technical here.

[paul cottingham]

I use tried and true almost exclusively, as I have a daughter who is very sensitive to chemicals. I often put it under shellac.
the key is to put it on really really thin. Rub it in with a cloth after it has sat for a bit. Works great.
it helps to warm it first, especially the finish that has beeswax in it.

[Jacob Reverb]

Edible linseed oil is not polymerized,and I don't know if it would effectively dry or not. I started using edible linseed oil(flax oil) in my varnish since it is a LOT clearer than the hardware grade oil. BUT, it needs to be polymerized. This is dangerous if you aren't experienced. You MUST work out doors. Use a DEEP container. Oil can get too hot and suddenly foam over the top in an instant,turning into a LARGE ball of fire before you can get the pan off the hot plate.

I AM NOT RECOMMENDING THIS AS IT IS DANGEROUS,TOO,but,I used to saw the top off of an EMPTY,EMPTY propane bottle to get a real tall container. You can blow up the container if any gas is left in it,so I cannot recommend it.

I'd carefully SIMMER the oil and not let it get past simmering for about 20 minutes. It would turn a rich,golden color(from the pale color it was before). Then,the oil was polymerized,and would then be a drying oil. Do not eat it after it is polymerized!!!!

After the oil was golden,I'd add the resins,and carefully simmer it till a drop gotten on the end of a longish stick,would make gossamer cobwebs when touched and pulled away from a bottle. That means the varnish is done. I'm not getting too technical here.

That's great information, George. Thank you! http://s3.amazonaws.com/advrider/beer.gif

[Zach Dillinger]

The food grade stuff will dry. You just can't flood the surface of the wood and you have to rub it into the wood. I do this often.

[David Keller NC]

I would like to buy boiled linseed oil WITHOUT the petrochemical dryers. Just raw oil that is "boiled".

What can you tell me about stand oil? Does it noticeably decrease dry time? I have seen BLO thicken from sitting in an open container for an extended period of time, its that similar?

Generally speaking, "boiled linseed oil" doesn't have petrochemicals in it (despite what the Wiki article says). The old-school method that period sources refer to (all the way back to the 16th century) had lead oxide added as a metallic drier. Modern "Boiled" linseed oil uses non-hazardous metallic salts as driers - typically zinc oxide or zinc carbonate. These can be purchased as "Japan Drier" if one wants to make their own.

The principal difference between linseed oil polymerized by exposure to oxygen, heating and exposure to oxygen, or exposure to UV (sunlight) is that the polymers that form in the liquid are of a different chemical structure than metal-catalyzed polymers in commercial linseed oil. These polymers form a finish that typically takes much more time to dry than metal-catalyzed BLO, and the resulting finish is typically much softer.

And - George is dead-on about the dangers of making your own "short-oil varnish" - made by heating linseed oil or heating linseed oil and dissolving tree resins in the hot oil. Because the polymerization of linseed oil in the presence of oxygen is highly exothermic (produces heat), the reaction can quickly get away from you, leading to 3rd degree burns, a house fire, or both.