Now you have a battery, you have a better chance of doing larger specimens of medals than in the apparatus described in the last chapter. Your battery and typing vessels are distinct. For small objects a jam-pot will do; for larger you get more room by making a rectangular box, which if lined and made water-tight will do very well. This can be done by painting the inside with philosopher's paint, taking care to put a large quantity of it along the joints, so there is no opening for the liquid to get out; or it may be lined with thin sheets of guttapercha. Fill your trough with a strong solution of sulphate of copper. Pour in a small quantity of sulphuric acid, and tie up a few crystals of sulphate of copper in a muslin bag, and hang in the upper part of the trough just below the surface of the liquid; or better still, put at one end a perforated shelf of a thick piece of gutta-percha, and put the crystals on this. Prepare your mould as directed in last chapter, with gutta-percha; attach a copper wire to the back of it. Do not forget to breathe on the face of the mould; then brush it over with some blacklead, not thickly. Bend the wire so that it comes just to the front at the top of the medal, so that it may touch the blacklead. Put it into the trough of solution. Opposite to the mould, but not touching it, put a plate of copper. This must be attached to a copper wire, and joined to the copper end of the battery, and the wire from the mould to the zinc end of the battery. If you are using one cell, leave it for two days; if you use two or three, somewhat less time will do, unless you require a very thick deposit. Before taking off the mould, remove the conducting-wire, and then lift it off by means of a thin penknife. The electrotype may afterwards be heated in a clear fire to redness, and then allowed to cool gradually; this will make it tough and workable. When cool, plunge it into a cold mixture of sulphuric acid and water. After being so immersed for a few minutes, take it out and rinse thoroughly in water; then dry it. You can then turn it up, and mount it in any way you desire. The back can be filled to give it solidity. This you can do by taking a stiff brush and rubbing the back over with a strong solution of ammonia chloride; then sprinkle over a little powdered resin. Then apply the blow-pipe to the solder; it will soon melt and run over the surface. If you wish for a full backing, pour into this some molten lead. Before mounting, polish up the face of the medal with rotten stone and oil, and finish with rouge put on with a soft brush or the tip of the finger.