Introduction of lead in oil

[Kenneth Freed]

George,
If you have a moment, could you comment on the introduction of lead by the old masters in heat bodied oil, linseed oil, walnut oil.

1. Specifically, would they have been able to introduce lead into the heat bodied oil from cooking the oil in contact with a piece or pieces of lead? Would this have to be a specific temperature?

2. Could they have added lead to the heat bodied oil by simply squirting a little lead white paint into the pot and at what temperature would this work (meaning combine)?

3. Would there have been a way to introduce lead into a cold temperature flax seed oil that has been cleaned of it's foot?

4. Would they have been able to add lead to a sunthickened linseed oil during the sunthickening process by using lead trays or with simple physical contact with lead sheeting?

5. Any other comments concerning introduction of lead for siccative purposes would be appreciated such as the relative amount of lead to oil to reduce drying times.

[George O'Hanlon]

Originally posted by Kenneth Freed:
1. Specifically, would they have been able to introduce lead into the heat bodied oil from cooking the oil in contact with a piece or pieces of lead? Would this have to be a specific temperature?

Metallic lead has almost no reactivity with vegetable drying oil, such as linseed oil, even at elevated temperatures. This was understood, because most recipes specified litharge or lead(II) oxide (PbO) or minium (red lead) or lead tetroxide (lead(II,II,IV) oxide, Pb3O4), which is reactive with drying oils. Oxidized portions of metallic lead may react, and impure lead ore contains much lead oxides, so this may have succeeded in forming a dryer, but comparatively small amounts of metallic lead would be suspended in solution, and would have precipitated once the temperature returned to normal levels.

Originally posted by Kenneth Freed:
2. Could they have added lead to the heat bodied oil by simply squirting a little lead white paint into the pot and at what temperature would this work (meaning combine)?

Lead white has little reactivity with drying oil to form a dryer with the oil, although it does lead soaps with vegetable oils.

Originally posted by Kenneth Freed:
3. Would there have been a way to introduce lead into a cold temperature flax seed oil that has been cleaned of it's foot?

No, not into solution with the oil. To solubilize lead oxide in oil requires processing to at least 250 degrees.

Originally posted by Kenneth Freed:
4. Would they have been able to add lead to a sun-thickened linseed oil during the sun-thickening process by using lead trays or with simple physical contact with lead sheeting?

This is one method, but it is unlikely much metal was solubilized into the oil.

Originally posted by Kenneth Freed:
5. Any other comments concerning introduction of lead for siccative purposes would be appreciated such as the relative amount of lead to oil to reduce drying times.

The simplest method, which was employed since medieval times, was to simply heat the oil with lead oxide.

[Lala]

very interesting!
I used to put a tiny pinch of red lead into the oil that I left in the sun for two weeks, but I guess the temperature wouldn't get high enough for it to have any effect?

[George O'Hanlon]

I did not say it would not have any effect, but that it would not make a drying oil, but rather a small amount may form a lead soap, but not enough to have a significant effect on the drying.