Part 11 (1/2)

_The Zinc-lio Vat_ It will be necessary to explain these words--Indigo blue is insoluble and cannot be used for dyeing If however it is ”reduced” or changed to indigo white, it has, while it is in this foretable and animal fibre These fibres will take it up from the solution and retain it If they are then exposed to the air, the oxygen acts upon the indigo in the fibre and turns it back again to indigo blue Various cheo white I propose to describe how the work is done with zinc dust and lients

In course of ti vessels theo dye liquor

By ”vat,” therefore, we understand not only the vessel used for dyeing indigo, but the solution of alkali salts of indigo white in water

This definition distinguishes the _indigo vat_ coo extract, or any other io o vat is better than any other for dyeing cotton and linen It is also very good for dyeing silk It has es over the hydrosulphite vat, as it is not nearly so es of temperature and weather It can be put to work after a six e which it shares with the copperas vat, though in a less degree, is that there is a sedi This is avoided by hanging a net in the vat after the sedi the skeins on rods

It is essential that the indigo used should be of the best quality, and ground to so fine a powder that it will float on water Coarsely ground indigo will never reduce and can be found at the bottohness is felt with the tongue Buy the best quality indigo ready ground, and if possible o and 80 of water, is a usual quantity If indigo powder must be used it must be round, fly about like dust The easiestwater into a jar (previously heated), then put in the indigo Close the vessel tightly The steao so that it loses its tendency to fly about

After 10 or 15 minutes it can easily be mixed with a stick The zinc dust should be dry and not caked

_The liht from a reliable chemist in a sealed container, and kept sealed till wanted

If it is cru it has been exposed to damp air, and is partly slaked already, and therefore o is more quickly reduced in a concentrated solution, a stock vat is first made and this is added to the dye vat as required

The vessel for the stock vat should have a well-fitting lid A stoneware jar with a bung will do very well To15-20 gallons use:--

10 oz Indigo 20 paste (or 2-1/2 oz indigo pasted with 7-1/2 oz of water), 1-1/2 oz zinc dust, 4-5 oz quick lime, 4-5 pints of water

Mix the zinc dust to a paste with a little of the water, gradually add the indigo and the rest of the water The heat of the water should be not less than 160F as it will cool while the li prepared Slake the li about 5 oz

of water over it When it begins to hiss and break, add more water little by little When all the lumps have cracked up stir till a thick even crearedients in the stock vat Stir well The stock vat should have a temperature of 120-140F

It should be stirred at intervals The vessel should be stood in hot water to keep the temperature as near 120F as possible In about 5 hours the mixture has a pure yellow colour and is ready to add to the dye vat (There is of course a blue-black scuo on top)

_Preparation of the dye vat_ The vessel used should be deep and upright so that an unnecessarily large surface is not exposed to the air, and a sufficient space for dyeing is obtained above the sedialvanised dust bin, or a barrel (provided it is not of oak or any other hich contains tannin), allons of water in the vat at a temperature of 65-70F In order to counteract the effects of the aten contained in the water of the vat, additions of zinc dust and lime are made some hours before the stock solution is added A pinch of zinc dust and an ounce of lime, previously slaked, should be added and the vat stirred

Stirringmade not to take air into the vat At the same time it must be stirred up from the bottom so that the sediment is mixed with the liquor above it The best tool for this purpose is a broom stick, to one end of which a piece of wood is nailed, like a garden rake When all is ready, carry the stock solution to the dye vat, and, to avoid splashi+ng through the air, hold it in the water of the vat while gently pouring out half its contents Stir up the vat and cover it until it shows a clear yellow colour under the surface of the scuood way to test the colour of the vat is to push back the scue of a saucer or plate, then dip it halfway into the liquor Against its white surface the colour of the liquor will be plainly seen It should look like good light ale If the liquor is greenish and sufficient time has elapsed, another pinch of zinc dust and a little ain stirred, allowed to settle and again tested

A little difficultythe vat to start, but once it has worked well no difficulty will be found in starting it again

It ork o does not penetrate easily, every effort must be hly scoured so that no particle of grease, size, or any other impurity is present Every effortitself to the cotton Never begin to dye in a vat which is greenish The unreduced indigo will attach itself to the stuff and be wasted Your ti it off

The vat should be thoroughly stirred and allowed to settle each day before dyeing begins When the sediment has settled, the froth should be carefully ski is finished

If a net is to be used it should be thoroughly wetted (if everything goes into the vat wet it will take less air with it) The net can be kept down by tying a few stones in a bag or an iron weight to the centre of it If the hanks are to be dipped on a rod this hted The hanks should not be less than 8 inches below the surface of the liquor and about 1 ft above the bottom of the vat The hanks should be turned after each dip, as, if the saoes to the bottom each time it will be darker A pulley over the vat to draw out the rod or net is convenient The dyeings can then be allowed to drain a few seconds Then wring each hank, shaking it out to get the air into it After a sufficient airing, dip again

Many short dips with airing betill produce faster colours Dip 1and air 4 minutes Dip 5 minutes, and so on

As linen and cotton look so very much darker et than when dry, a bit should be dried to judge if the colour is right

Indigo can be dyed from the palest sky blue to black The very palest shade of sky blue is never very fast The virtue which indigo alone seehter with continual use, it also becomes a clearer and more lovely blue This is especially so on cotton and linen, for which it is a superb dye The varying shades of indigo of butchers' coats, sailors' collars, and French porters' blouses always give us pleasure

CHAPTER XI

THE DYEING OF SILK

Silk is covered with a natural guin This is done by boiling for one hour orsoap, 2 to 8 ozs to the pound of silk according to the aum on the silk It is then ashed, and is ready for