To solder a joint in a watch case, the old joint must first be filed off clean. This should leave a semicircular groove in which the new joint can lie true. The joint is cut from drawn silver or gold tube. Place it in its groove, having first wetted it with borax paste and water. Along its side place a long thin strip of silver or gold solder, and apply a blowpipe flame to the case near the joint until it is well hot; then direct the flame on the joint until the solder runs. As soon as the solder sets, and while the case is hot, plunge it into a pickle made of sulphuric acid 1 part and water 9 parts, then wash in plenty of water, and clean up. B lore soldering, unpin the back, bezel, and dome, and take out the bow, push piece, and any steel springs so that they may escape injury from the heat.