Working with filler is more the job of the painter than of the panel-beater. This is only suited for covering up small damages anyhow. Even though one can also reproduce missing edges quite skillfully, indeed, the durability of metal can never be achieved. Thickly applied filler is generally the work of a layman, particularly as nowadays, one can later measure the layers without damaging the paintwork. Even if the surface repaired in this fashion looks perfectly done, in the event of a small bump, there won't be any metal denting, just a cloud of dust. In a professional repair-job, the bodywork is returned almost to the original shape by panel beating, any further improvements are then done by tinning. In the event of greater temperature differences this also provides a flawless join between the original- and the filler material. Joints and seams which occur in the manufacturing process can also thus be reproduced. The working temperature of the tin lies just above the baking temperature of the paint and way below the heat that would deform the metal components.
One condition for all work with cold solder, is a good preparation of the metal to be tinned. If the dent(s) have been beaten out as far as possible, and the entire area to be processed has been freed from all possible alien substances, the tinning paste can be applied with a brush. The temperature of between, slightly under 200°C and just over 250°C, can be achieved by using an oxy-acetylene torch adjusted to a soft flame or a blowlamp. The treatment can be continued when the paste turns brown (figure 1). It must then be wiped clean, so that the tin content in the paste becomes visible. This forms a good base for the next layer. The alluvial tin can also be applied astonishingly well to vertical areas using tin-rods (figure 2). A constant (not too high!) temperature of the working surface and the material is important. Due to the approx. 25 % tin portion, the material remains doughy over a wide temperature range. However, due to the high lead content, problems can arise. Care must be taken not to inhale the vapour and to wash your hands thoroughly afterwards, any left-overs must also be disposed of properly. Wooden soldering blocks, treated with a lubricant against burning, enable the lead/tin alloy to be distributed more easily (figure 3). The blocks are available in various shapes and diameters for the shaping of the car body contours. After the repair area has cooled down slowly, further work, e.g., with a coachwork plane, can be carried out (figure 4), until the surface is smooth and shows no transitions. The spray painter may possibly apply another thin layer of filling before the final finishing is done. 05/11