Casein found more favour as a material for pens in Britain than elsewhere. Sheaffer used it briefly in America, but otherwise, so far as I know, pens were not made from it there. In Britain, Burnham and Conway Stewart used it extensively.

From 1900, casein was sold under the commercial names such as Galalith and Erinoid and was used to manufacture buttons, such household items as clock cases and desk sets and, of course, pens. Though it did not mould well, it could be machined with ease and its main attraction was how well it took colouring, whether as a surface dye or throughout the material. The colours were strong and the material appeared to have exceptional depth of pattern as well as taking a high polish.

It was supplanted by celluloid which was, in almost all respects, a better material, but memory of the lustrous colours that could only be achieved by the use of casein led to its revival. Conway Stewart used it for several ranges of brightly coloured pens both before and after the war, and Burnham made much use of it in the post-war period.

It is well known that casein and water don’t mix. Immersion in water for a few hours will ruin such a pen. It will expand by about 10% and soften, and it will distort on drying out. That’s not to say that we should overreact about it. A wipe with a damp cloth won’t harm a casein pen, but there is good evidence that use in a highly humid climate can lead to deterioration.

Related to the above is another major problem with casein – crazing. This surface cracking is a result of exposure over a long period to light and dampness. The cracking goes quite deep and cannot be polished out. It is unsightly and spoils the lustre of the pen. Jonathan Donahaye, the late, great Conway Stewart collector, believed that those casein pens that we now find in perfect condition are the ones that were forgotten in the back of drawers. There’s every indication that he was right, and therein lies the clue to keeping your casein pen in good condition. Keep it out of bright sunlight, keep it dry, and store it in a dark, dry place when it is not in use. Otherwise, use it and enjoy it – that’s what it was intended for!

How do you know whether your pen is celluloid or casein? Dump it in a basin of water and wait for two hours. No! Really! Don’t do that! Supposedly, casein smells of formaldehyde whereas celluloid smells of camphor. Also, if you rub casein briskly, it gives off a milky smell. I have to say that these tests don’t work very well for me. If you have a brightly coloured post-war Burnham, chances are it’s casein. Several ranges of Conway Stewarts, including the 475, 15, 759 and several Dinkies and Dandies (by no means a comprehensive list!) contain casein models. If the colours are strong and the pattern appears to reflect light from the depths, chances are it’s casein. Against that, remember that even among Conway Stewarts, celluloid is much more common than casein. Perhaps the best answer is to treat all your Conway Stewarts and Burnhams as if they were casein. Then you’re safe!