In the article Madder, page 32, I mentioned having made an extract similar to the Adrianople red.  For which purpose, a sufficient quanitity of the roots should be taken fresh out of the ground, washed clean from the dirt, bruised in a mortar, and then boiled in rain-water till the whole becomes tinged of a red colour, then put into a cloth and all the colouring matter pressed out.  This should again be put into hot water in a clean glazed earthen-pan, to which should be added a small quantity of water in which alum had been dissolved, and the whole stirred up together; then immediately add a lump of soda or pot-ash, stirring the whole up, when an effervescence will take place, the allum that had united with the juice of the madder will be found to become neutralized by the pot-ash, and the result will be a precipitate of the red fecula.  This may be washed over in different waters, and either put by for use in a liquid state, or filtered and dried in powder or cakes.  Most vegetable colours will not, however, admit of being extracted by water, and it is necessary to use an acid for that purpose:  vinegar is the most common.  But in making the extract from roots with acids, great care should be taken that they are sufficiently cleared from mould, sand, &c.; for, if the same should contain either iron, or any metallic substance, its union with the acid will cause a blackness, and of course spoil the tint.  In a similar mode are all the different colouring principles extracted, either from leaves, flowers, fruits, or woods.  The preparation of woad is a curious process on similar principles; which see in page 31.

Weld, or dyers weed, is generally used after it is dried.  The whole plant is ground in a mill, and the extract made by boiling it.  It is then managed with alum and acids agreeably to the foregoing rules, which are necessary for throwing out the colour.

Instructions how Substances may be tried, whether they are serviceable in Dyeing, from Hopson’s Translation of Weigleb’s Chemistry.

“In order to discover if any vegetable contains a colouring principle fit for dyeing, it should be bruised and boiled in water, and a bit of cotton, linen, or woollen stuff, which has previously been well cleaned, boiled in this decoction for a certain time, and rinsed out and dried.  If the stuff becomes coloured, it is a sign that the colour may be easily extracted; but if little or no colour be perceived, we are not immediately to conclude that the body submitted to the trial has no colour at all, but must first try how it will turn out with the addition of saline substances.  It ought, therefore, to be boiled with pot-ash, common salt, sal ammoniac, tartar, vinegar, alum, or vitriol, and then tried upon the stuff:  if it then exhibit no colour, it may safely be pronounced to be unfit for dyeing with.  But if it yields a dye or colour, the nature of this dye must then be more closely examined, which may be done in the following manner:—­