Rimino

Filtering Boiled Linseed Oil

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Does anyone know how to filter hot linseed oil after it is boiled; I heard it being done after cooking it with sandarac.  I tried it with a cotton cloth but it never sank through.  Thanks a lot

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I can get just about anything to go through a coffee filter (which is much finer than a cotton cloth) in a day or so, by thinning it with the appropriate solvent.

Yes, some of the solvents I have used are potentially toxic, so appropriate precautions may be in order.

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I don’t know the temperature, but it is hot enough that steam flows from the surface and if I would get it much hotter it will catch fire.  I try to filter it at this temperature.  When cooled the oil is thick and stringy.  I try to stay away from solvents; even when I use them safely, they still bother me, although I sometimes add a small amount of oil of turpentine, but just a little.  Do you need a solvent to pass the oil through a filter? 

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4 hours ago, Rimino said:

I don’t know the temperature, but it is hot enough that steam flows from the surface and if I would get it much hotter it will catch fire.  I try to filter it at this temperature.  When cooled the oil is thick and stringy. 

I think it's rather important to know how hot and how long you cook things.  Sounds like you are making stand oil.  What is your intent in doing the cooking?

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2 hours ago, Don Noon said:

I think it's rather important to know how hot and how long you cook things.  Sounds like you are making stand oil.  What is your intent in doing the cooking?

I cook a couple of hours.  My intention is to make stand oil, and I succeed, but sometimes I need to filter out impurities.  Do you know if you can filter hot stand oil?

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I never tried stand oil, but I would expect it to filter through almost anything, but extremely slowly for the finer filters.  There would be the problem of keeping it hot for as long as it takes, perhaps days.

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You didn't cook it with sandarac, right? 

If not you must have cooked it pretty hot, almost to the point where it starts to gel, I'm guessing. Steam appears at lower temps, smoke appears at hotter temps, are you sure it was steam? Got a thermometer?

I have never had a problem with cooked oil passing through a filter unless I have added some kind of resin.

Have you tried washing it in water? Not hot of course.

I think if it is cooked so much that it is hot and stringy that you have gone too far. Even solvents are not going to prevent it from starting to congeal.

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1 hour ago, DonLeister said:

You didn't cook it with sandarac, right? 

If not you must have cooked it pretty hot, almost to the point where it starts to gel, I'm guessing. Steam appears at lower temps, smoke appears at hotter temps, are you sure it was steam? Got a thermometer?

I have never had a problem with cooked oil passing through a filter unless I have added some kind of resin.

Have you tried washing it in water? Not hot of course.

I think if it is cooked so much that it is hot and stringy that you have gone too far. Even solvents are not going to prevent it from starting to congeal.

I’m not using any resin, just oil.  It gives off steam and not smoke.  It doesn’t gel, just the consistency of honey when cooled.  If I wash it after it is cooked it won’t dry well will it?  I do wash it before I cook it.  I forgot to say I wet with water and forcefully wrung out the cloth first, in case it might catch fire from the hot oil.

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Maybe the wet cloth isn't helping? Wash it before cooking, not after. Can you keep the oil warm while it if filtering, maybe with a light bulb of some kind-incandescent?

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39 minutes ago, DonLeister said:

Maybe the wet cloth isn't helping? Wash it before cooking, not after. Can you keep the oil warm while it if filtering, maybe with a light bulb of some kind-incandescent?

Thanks for the idea; I’ll think of a way to do this, and if I can’t I’ll keep in mind the the metal mesh coffee filter.

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12 hours ago, Rimino said:

  I forgot to say I wet with water and forcefully wrung out the cloth first, in case it might catch fire from the hot oil.

A water-wet cloth will have zero effective permeability to hot oil. Before it dries enough that it SHOULD have worked, the hot water will have caused the oil to harden in contact with the fibers - so still impermeable. That's how they made rainclothes in the old days.

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In the interest of clarity: stand oil is processed in a vacuum and is fully polymerized but not oxidized.  What you are making is a heat bodied oil.

Joe

 

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On 1/2/2019 at 11:45 AM, Rimino said:

Does anyone know how to filter hot linseed oil after it is boiled; I heard it being done after cooking it with sandarac.  I tried it with a cotton cloth but it never sank through.  Thanks a lot

What works for me with dirty, gritty oil is to use a piece of window screen first to catch the big pieces of dirt and after reheating to hotness again I use a mesh material that has half the size of window screen holes for a second run through.  This white colored mesh material I speak of can be found on the outdoor christmas angels, snowmen, deer etc. that are placed out in the front yard during the holiday seasons.   Make sure the oil is hot, use gloves and one time each should be enough.   I don't filter until the entire cook has all ingredients together and up to temperature for an efficient pour though filters.  

I have to filter out the lime residue and dirt from melted lead for the most part - I don't use sandarac. 

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You do have the most amazing hardware store I have ever seen with in walking distance of your house,,,,, I have not only ever seen, but ever dreamed of,,,

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It's fortunate for me to have such a good hardware store nearby. Run by knowledgeable trades people. Have you used the wire cloth to filter anything yet?

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