material I use is thin brass or tea-cans ( about 0.2 mm thick ) . Aluminium
is impractical because you cannot weld it (in the scales of modeling) .
But it is possible to make individual parts. If you revert to my pages,
tea-cans were used in the body of the taxi. In the car body repair shop
diorama, the FIAT 131 is made of thin brass sheet and the hood+mudguard
panels of the Renault 5 plus the wrecked body panels here and there
are made of aluminum sheet. I prefer aluminum for ease of copying. In the
car body repair shop diorama, I duplicated the panels from other plastic
models and crushed them. If you use suitable thickness ( or thinness???)
, then all you have to do for crushing is to hold the pice between your
fingers and push it against something . It then needs small retouches to
look like the real crushed body panel.
If you work with separate panels, then you can join them with a reinforcement slab at their backs, using superglue (cyanoacrylate = CA ) . But that will be a very tender model and cannot withstand ant surface refinement treatments like filing and sanding. To endure the forces, you have to use tin or brass sheets. The only way to make them strong is by soldering and then machining.
Tin is , in my opinion, a very friendly material to work with , since it can withstand harsh handling while building. Since it is strong, you can make thin structures that can hold themselves, whereas if made with e.g. plastics, would have to be much thicker.
So, enough for praising tin ! Now, how do I shape it? As you know, every 3-D object has -what is called- a "development " that is what you get when you open up the sides of the object and lay it on paper. First of all, I draw the development . I sometimes first practice it with paper to see my way and then proceed to cutting it out of tin.
Then comes the bending process. I use hand tools ( like pliers ) for all bendings and frequently use hammering ( light, of course ) to keep the metal in the proper shape. I then use solder to fill the joining edges of the metal. I use solder to make fillets inside the bends. For example, if a smooth shouldered bend is to be made, and if I foresee that it will be too tedious because that bend should take place in two planes ( e.g. bending toward left while simultaneously going downwards ) , then I approximate the bend in small straight sections, fill it with solder inside, then grind it to the final shape.
Separate pieces are manufactured and still bonded with solder (generally, I mean; sometimes I use cyanoacrylate if solder is inevitably has to be in view inesthetically). For the surface finish, I use automotive putty for final filling and sand it with up to 2000 grain sandpaper. The rest is applying paint; first the primer and next the final coats.
Other materials to use may be anything that is messing around - that is the soul of scratchbuilding. The most common materials are wood (balsa preferred for easier shaping) , plastic sheets, textiles, cardboard, or parts of anything that is in our daily use ( the refills of Parker ball-point pens are very nice for chrome-plated exhaust pipe ends , for example).
You name the material, it will do for something. The material need not be scrap though; let me tell you a memorial:
When I was a teenager, I needed a piece of sponge urgently and found it inside a mattress and the next move I made was to cut the edge of the mattress ! My mom did not think the way I did .... She never realized that she would never have a scrap mattress if I hadn't cut its edge!