Dear friends,
recently, I was fortunate enough to find a full 1915 issue of the "Kunststoffe" magazine I mentioned before, so I'd like to share a translation of the full article on painted replacement helmets for completeness:
Military helmets made of felt, paper pulp or metal
With the large quantity of military helmets needed for war purposes, it was necessary to refrain from making them of leather for 2 reasons. 1. because this became scarce and 2. because the production of impeccable glossy coatings is too time-consuming and therefore too costly work. Felt helmets are made by dies and then coated with an easy and quick drying opaque black primer paste in oil. As a rule, several primers are necessary because the substrate is very porous. The individual coats are sanded with pumice powder after hard drying (at approx. 60°C). The last coat is treated with a less hard abrasive, such as gur or tripel, so that it gets a weak, uniform gloss. Then the helmets are sprayed over with a black oil gloss paint or field gray oil matt paint. If no gloss at all or only a low gloss is required, the number of primer coats can be limited as far as possible, which makes the process considerably cheaper. In an analogous way, the helmets are made of brown elastic paper pulp. Before painting, they must be carefully freed from dust and sanded clean, which saves on primer material, since in the other case the paste must first level out unevenness. Since brush painting is too time-consuming and gives too uneven results, spray painting is used almost exclusively for mass production. Dip coating is also often used for military helmets. Since in both cases the substrate is sensitive to fire, only light and fast-drying oil-based paints can be considered, but their coatings must be water- and weather-resistant. Helmets made of felt or paper painted in this way should be almost as elastic or insensitive to impact as leather helmets. Attempts have also been made to produce helmets from black plate, which were painted black or field gray after priming. It remains to be seen whether these experiments can be transferred into practice.