Weld Lines
August 27th 1996

Hey what do car guys need to know about weld lines for? True, making weld lines are mostly for the armor guys but this technique is used sometimes in car models. Some applications are exhaust systems, roll cages and frames. Just another area to make that model more realistic.

Seceral techniques that can be used
1. Two part putty
2. Masking tape
3. Pyrograph (sp?)
4. Syringe
5. Stretched Sprue


Mix some two part putty and roll into a thin long roll (Fig 1a, 1b, 1c) With some dental tool or exacto knife apply the putty to the model. Not an easy technique to learn but some swear by it(fig 1d) Hardest part is to get the roll of putty the same diameter the whole length.


Lay down two strips of masking tape where you want the weld (fig 2a). Lay down some putty (fig 2b). Wait a bit then pull the tape off (fig 2c). The putty remaining will have to be worked with a tool to get a more weld like look. A simple technique but will only work on flat areas. Great for long straight lines

This is a tool like a soldering gun that melts the plastic. I haven't tried this method but is appears that you need a lot of skill and practice to get this method right. Note that since you aren't adding any material the weld lines can not be raised.


Putty is loaded into a syringe and squeezed out to make the weld line. You have to move the syringe up and down to get the weld look. The diameter of the syringe is the diameter of the weld. The only putty I found to work for the syringes I have is Squadron White. Any other syringe was too thick. Other syringes may work better or you may have to thin the putty. An easy method to use and master.


Stretch some sprue. Dip it in some plastic glue or lacquer thinner. This will soften it and you can apply it to a model with a dental tool or exacto knife. The diameter of your stretched sprue is the diameter of your weld. Also an easy technique to learn and use. The diagrams show instead of stretched sprue that Q-Tip shafts are used. These are also styrene and when you stretch them they retain their hollow nature. This is helpful in when you dip the sprue into the lacquer thinner (or glue) the lacquer attacks from the inside and outside so it softens quicker.

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