199 Chapter 9 Nonstructural Panel Repair Copyright Goodheart-Willcox Co., Inc. separated hardener. See Figure 9-54. Squeeze out the proper amount of hardener next to the filler on the mixing board, Figure 9-55. Use a clean paint stick or paddle to stir the hardener and filler together. Continue to stir until the filler is a uniform color, with no streaks of hardener or unmixed filler. The filler is now ready to be applied in the low area. The curing of the mixed filler produces heat, which can be felt on the mixing board. The curing process begins as soon as hardener and filler are mixed. The mixed filler will stiffen as it cures and will only be spreadable for a few minutes. Therefore, it is important to apply the filler as soon as it is mixed. Once the mixed filler has cured too much, it is not workable. Never return mixed filler to the can. The mixed filler will contaminate the unmixed filler. Use a clean spreader to apply a thin coat of mixed filler to the low area. Apply the body filler within the featheredged area. Press down hard on the filler as the first coat is applied. This will squeeze out the air from under the filler and reduce the number of pinholes. Pinholes are pockets or voids in cured filler. Apply addi- tional coats of filler, building up the filler until an overfill (filler higher than the surrounding metal) is achieved. After overfilling the low area, use light strokes with the spreader on the filler to obtain a smooth surface. Stop working the filler when it begins to stiffen. Allow the filler to cure. Shop temperatures below 60°F increase cure time. Clean the mixing equipment while the filler is curing. Filling a body line can be difficult. A simple body line can be filled by spreading an overfill on the peak of the body line. A complex body line can be repaired by forming the filler to match the contour of the undam- aged body line. A body line sander can be used to mold the filler. Put 2″ (50 mm) masking tape over the contour sander that best matches the shape of the original body line. Apply the mixed body filler to the damaged body line and press the body filler into the proper shape with the contour sander. Hold or tape the contour sander in place until the filler hardens. When the filler has hardened, remove the sander. The filler should be shaped so it requires little sanding. Most problems are caused by the filler or hard- ener itself, the mixing procedure, or the condition of the application site. To avoid problems, follow these guidelines: • Check the manufacturer’s date on the filler can. If the filler is over one year old, do not use it. This rule applies even if the can is unopened. • If runny liquid hardener comes out of the tube after kneading, do not use the hardener. • If the metal is below 70°F, warm the metal with a heat lamp before applying the filler. • If the metal is damp, use a heat lamp to warm and dry the metal before applying the filler. • Follow the recommended mixing procedures. Too much hardener, which is evidenced by a deeply colored mixed filler, will cause pinholes and a lack of adhesion. Too little hardener will cause an insufficient cure (soft filler) and a lack of adhesion. • If the filler is to be applied over bare metal, use a grinder or 80-grit sandpaper to remove the paint. CAUTION Goodheart-Willcox Publisher Figure 9-54. Kneading the hardener tube will mix the hardener. Goodheart-Willcox Publisher Figure 9-55. Body filler and hardener are combined on a mixing board. Filler Hardener