(English Mechanics.)

Blueing Steel

(1) Make a box of sheet iron, fill it with sand and subject it to a steady heat. The articles to be blued must be finished and well polished. Immerse the articles in the sand, keeping watch of them until they are of the right colour, when they should be taken out and immersed in oil ( Amateur Mechanics).

(2) ;A common method of blueing small steel goods by dipping is to melt saltpetre in an iron pot ; then immerse the previously polished and cleaned articles until sufficiently blued, remove and cool at once in paraffin oil, and afterwards dry out in sawdust (Workshop Wrinkles and Receipts).

(3) ;Use a piece of sheet iron forming a small table with a powerful gas burner under the corner. Spread the work on the plate, so that it gradually heats, then push one at a time to the hot part, but as soon as it shows the colour required, remove it to the cooler part and push on to a cold plate. Some clock hands are blued with a coloured varnish.

(4) ;To a thimbleful of Canada Balsam add as much turpentine as will fill a full-sized wine glass ; thoroughly mix. Add Prussian Blue which has been ground very fine in turpentine till the desired colour is obtained. This varnish dries in half an hour, and two coats may be given if one does not suffice. An excess of Canada Balsam will cause stickiness when dry ( Amateur Mechanics).

(5) ;The usual method is to heat the articles to a certain temperature until the blue colouring appears, and then immediately plunge them into water. The heat of the article determines the colour, and by carefully regulating the temperature various colours from purple to straw may be obtained. There are many objections to such a blueing method. The articles must not contain anv other metal or be soldered. Considerable carbon must be in the steel in order to bring out a good colour. Sort steel does not colour as well as that high in carbon. Then, too, large quantities must be treated in order to obtain a satisfactory result. A few pieces are very difficult to treat, and good results are not obtained. A special furnace is also required for this work. To overcome the objections referred to the following method is recommended by " The Brass World."

Make the following solution :-

Water, 1 gallon.

Hyposulphate of Soda, 2 ounces.

Acetate of Lead, 2 ounces.

The hyposulphite of soda need not be chemically pure, as the ordinary commercial article answers perfectly. The acetate of lead and the hyposulphite of soda are dissolved in the water. The whole is then heated to boiling. At first a white percipitate is pro- duced, but later, as the temperature rises, it is changed to black. When nearly boiling it is ready for use.

The steel to be blued may be used without being coppered or brass plated, but a slight film of copper or brass greatly enhances the brilliancy of the colour. If the steel is used without a copper or brass i deposit the result is perhaps more like that of heated blued steel. Whether to use the steel in one condition or the other remains with the operator. If desired the steel may be dip-coppered. This seems to answer as well as the heavier deposit in producing the brilliant blue colour. The steel, either bare or plated, must be uniformly clean before it goes to the bath, as otherwise the results are not uniform, and streaks or spots will be present. Such a mottled . effect, however, is frequently not undesirable, as it resembles to a greater or less extent the colour which is found on case-hardened steel. Iron gives equally as good results as steel.

When the steel is cleaned it is dipped into the hot bath of " Hypo and sugar of lead," previously given. At first the colour is golden, but in a moment it changes to a dark red, and finally a blue colour is reached. This takes but a few seconds, so it must be carefully watched in order to remove the article at the proper time. When the required tint has been produced the article is rinsed and dried. A coat of lacquer is given it. If the article is left in the solution too long a grey colour is produced, and finally a greyish black. These last two colours are not particularly useful, although they may be of some value for cheap work.

This bath is now being used on brass and copper, and works excellently. Small articles are often made of brass, and then given a blue colour in this bath to resemble steel. If the colour that is obtained upon the steel itself is not sufficiently brilliant a light copper deposit either by dip coppering or by depositing may be given it, when the most brilliant blue possible to obtain by any pigment will be produced.

(fowler's Mechanics' and Machinists' Pocket Book.)

Steel. Blackening Polished Steel

Take an iron pan or vessel, heat in it ten parts of saltpetre and one part of black oxide of manganese, all by weight. Stir the articles in this at a good heat, as much as they will stand without damage, and until the desired colour appears. Take out and wash well when cool, in hot soda water, rinse well in clean hot water.

Copper. To Colour Copper

Black : Clean the copper with emery or glass paper, heat gradually in a spirit flame, dip for 10 to 15 seconds in a solution of copper filings, and dilute nitric acid, and heat again.

Bed : Gradually heat in hot air; as soon as the desired colour appears, quench in cold water; the copper should firstly be well cleaned.

Orange : Clean well and dip into a solution of crystallised copper acetate.

Violet : Clean well and place in a solution of antimony chloride, rub afterwards with a cotton cloth; keep the copper, while treating, at a temperature of about 120°F.

Crystalline Appearance : Boil the copper article in copper sulphate solution.