Casting preparation before painting

Does anyone have any information on how the factory prepared casting for painting? I have seen references to 'conditioning' but never any details. I use etch primer when restoring then cellulose paint. I don't think paint would adhere to bare metal very well, but I am ready to be disabused

Hi Chris,There is little informaion about how the models were prepared before painting. What I know is that after casting the models were de-bured in a rotating barrel, they were mixed with small abrasive chips and they came out polished. After this they passed through what Meccano called the bounding machine. deburing at BobignyIn this machine, the castings were dipped in a hot bath of sauda then they were rinsed and dried. The object of this treatment was to make some tiny holes in the castings so that the paint would stick. Meccano did not use any primer, there was only one coat of paint. bonderising machine at Binns road bonderising machine in BobignyI hope that this will answer your question, if not please shout.

Fascinating information Jaques - thank you. I initially tried enamel paint on bare metal diecast but the edges of windscreens etc did not cover. I spoke to a friend who has a business repairing real vehicles who advised me to use etch primer, which achieves the effect of multiple very tiny 'holes' in the casting to which subsequent paint will stick. I have used this ever since and more recently cellulose paint with some success. Thanks again ! Chris