Homemade Megilp

[Allan Rahbek]

Hi,
I have found out how to cook Black Oil without it being black.

The trick is to cook it with water. The water will prolong the cooking process and secure that the temperature don't overheat so that the oil becomes dark.

I attach two examples: the light is linseed oil cooked with litharge (lead) and water. When I use it I mix the oil with Mastix Varnish 1:1

The other (dark) is Black Oil with bees wax kept in a tube, don't need mixing. It is nice to use but miscolors the paint when used, though it stays that way and don't yellows later. It also adds the quality of flexibility to the paint.

The light black oil can be mixed with wax also, I guess.

[Richard Bingham]

Right you are, Allan. Temperature control is the most important factor in making a pale "black oil". Linseed oil easily turns coffee-colored or darker when overheated.

Worth noting is that aluminum adversely affects lead/oil combinations, so cook your black oil in an enamelled pan, and if you tube these mediums, be sure the tube is coated. I'm pretty sure lead or tin foil tubes are no longer available anywhere . . .

Also, a drop of water facilitates the formation of gel when mixing the black oil with saturated mastic, especially at warmer temperatures.

[Allan Rahbek]

Originally Posted by Richard Bingham

Worth noting is that aluminum adversely affects lead/oil combinations, so cook your black oil in an enamelled pan, .

Yes, I cooked the oil in a stainless steal pot and let the oil boil as long as there was steam coming up, water evaporating, to secure that the temperature would not go higher than around 110 degrees Celcius.

[Richard Bingham]

Someday, I'm going to learn centigrade conversion . . . (doh! 110C . . . would that be about 230F ?)

I use a candy thermometer, to insure that temperature doesn't rise above 175 degrees Farenheit. (80C??) It's tempting to cook it hotter, as it can take upwards of an hour at this altitude, (5000 feet) and the litharge goes into solution much faster at temps above 175F, but will also turn darker, the hotter it's cooked. The "soup" must be stirred continually to keep the litharge from settling into a solid mass in the bottom of the pan.

The single time I cooked black oil with water, it appeared to me that steam boiling off really improved "agitation" and absorption of the litharge. Of course, there's always some precipitate when the oil cools.

Anyone who's baked a cake at sea-level, then tried it at a higher altitude knows how sensitive differences in ambient pressure and temperature can be. It takes a fair amount of experimentation to come up with an agreeable product!

[Allan Rahbek]

The Celcius degrees are. : 0 is when water freeses, 37 is human temperature, 100 water boil.
I guess that water boil at a lover temperature in the mountains, but that can not be of much importance if you know about it, just give it a little longer.

The good thing by using water is that you don't need a thermometer, you know that the temperature is just above 100 as long as the steam is coming up. It takes time for the water to evaporate so you just put a little more into the soup.

Yes, it is important to stir it all the time. Afterwards you will let it precipitate in a glass jar for several day's. When the superfluous lead has settled on the buttom of the glas you pour the oil in another glas bottle ready to use when mixed with Mastix.

[Richard Bingham]

For some time it's occurred to me to re-cook the precipitated "sludge" with new oil . . . but I haven't done it yet. Have you tried it? (litharge is getting tougher to come by . . . people worry we're building explosives!)

[Allan Rahbek]

I thought that lead was against bombs, as in nuclear!

I havn't reused the remains, yet, but maybe it's worth a try. If we add an ammount of fresh lead? The worst that can happen is that it dries sooner or later.

By the way, I plan to built some Flake White Oilpaint. As you may know it's not allowed here in Denmark, so it's very exciting stuff, but don't tell anybody, ssshhhh.

If I manage to do that I will use the coarser parts of it to make Megilp/Marogers Medium.

[Allan Rahbek]

By the way, how will you add water to Megilp / Black Oil? by adding egg ?

[Richard Bingham]

Allan, we're comrades in arms! I've been mulling my own white lead for several years, because I couldn't find a flake white that "worked" like what I was used to years back.

Mull your white lead in the black oil . . . I think you'll really like it!

You're right . . . biggest problem re-using the dregs is how to measure the quantity. That may not be much of an issue, since only a certain amount of litharge will go into solution in the oil anyway. ?? I don't know, but I'm inclined to try it. We'll have to keep in touch on this.

It only takes a single drop of water for a spoonful each of black oil and mastic to hasten the gelling process. Emulsions are something I've been promising myself to try, but haven't yet.

[Allan Rahbek]

Richard, could you start a new topic about making Flake White?