New York Jany. 11th 1808
I have had the pleasure of recieving your letter of the 3d inst. relative to the process of expressing the oil from the Bene seed there is very little difficulty in the operation. The common flaxseed oil Mill is the machine I used: great care must be taken to have it well cleansed. The method I pursued was in the first instance to put the Bene seed under press in its crude state without grinding or heating, and after pressing from it all the oil it would yield which appeared to be about one third part of the oil the seed contained.
The seed was then taken from the press and ground and heated and pressed again, but the oil it produced was not quite so fine and pure, it tasted a little of the flaxseed but it may be used for the table—it does well for the lamp and would probably do for painting.
If I was to make another experiment and had a new Mill or machine that was not impregnated with the flaxseed oil, I would first grind the seed and press it without heating, and then grind it again and heat it and press it again. By this process I should expect to get more than two thirds of the oil from the seed in the first operation of pressing which would be pure and good salad oil The second pressing after heating would produce inferior oil and perhaps in quantity about one third.
I have lately seen an extract from the transactions of the Bath Agricultural society in England from which it appears that the poppy has been cultivated in France, Flanders, and Holland, for the purpose of making salad oil for table use, and it has been fully proved that the oil made from the seed of poppy is sweet wholesome & nutricious, and that it does not in the least partake of the Narcotic property of plant. The white poppy is preferred but the blue yields most seed and the oil is quite as good.
It is said this oil is often mixed with the Olive oil and it is probable that a great proportion of the oil we use in this Country is of that mixed kind.
I am sir with sincere Respect Your most Obdt servt
DLC: Papers of Thomas Jefferson.