Modern Art Extract: Harden and the English chemist W. J. Young did an experiment in which a yeast extract, which could carry on fermentation, was put in a semi-permeable bag that was then suspended in pure water; small molecules from the extract could pass through the membrane of the bag into the water, but larger molecules remained in the bag. This process is known as dialysis. After dialysis, the extract within the bag could no longer carry on fermentation. However, when the water from outside the dialysis bag was added, the activity of the extract was restored.
Resist and extract printing. An old method of producing patterned fabrics, a variation of which is still in use, is the process known as resist-dyeing. It was employed when a pattern of small light motifs was desired on a large dark background in one color. The effect was produced by coating the portions of the fabric to be left white with wax or clay. The entire fabric was then dyed. Wherever the coating had been applied, the fabric "resisted" penetration of the dye. Upon removal of the wax, a white pattern was left on the dark ground. In modern art extract reproductions of this type of fabric, the procedure is exactly opposite from the former method, and is called extract printing. After the entire fabric has been dyed, a chemical is applied to certain portions, which removes the background color, and forms the desired pattern. In both methods, an effect of great charm is achieved by the slight irregularities and color variations in the finished product.
All cheese starts as milk, but the milk may be sweet whole milk, a combination of sweet and sour milk, or a mixture of whole and skim milk. The first step in making cheese is to separate the whey (the liquid portion of the milk) from the curd (the solid particles). When milk is slightly sour, this may be done by placing the milk over very low heat for several hours. In modern art extract manufacture, a culture of lactic acid-producing bacteria is added to sweet milk to cause the separation, and sometimes a combination of heat plus the culture and an extract of rennet may be used.
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