David Wells, vintage pen collector and dealer of primarily British writing instruments continues his discussion on a delicate material used by several pen companies in the past. Before the introduction of colourful resins and celluloid materials, fountain pens were made from vulcanised rubber with colour variations limited mostly to black , red or a variation of the two we call mottled, ripples or wood grains. Casein material was one of the first alternatives to provide a wide variation of colour and patterns.

Why casein?
Casein has been described as "the most beautiful of plastics" and was produced in a wide variety of colours including delicate pastel shades, pearls and mottles, especially those imitating tortoiseshell and horn. The material also readily takes a surface dye and this process was extensively used to produce fashionable colours at short notice and for two colour effects by selectively cutting back the dyed surface layer. Casein plastics take an attractive polish which can be achieved mechanically with abrasives (except for surface-dyed material) or chemically by immersion in hot, hypochlorite solution - known as dip polish.

a casein clock from 1930

The problems with casein
The manufacture of casein is a slow, batch process requiring the material finally to be hardened by immersion in formaldehyde solution - sections of about 25mm thickness requiring up to one year. Casein plastics are not readily moulded, although sheet can be pressed into a limited range of shapes, such as shallow bowls and candlestick bases, by 'hot stamping' . Instead, casein objects are fabricated from stock material such as sheet, rod or tube.

Conway Stewart 475

Casein does not seem to be an ideal material to make fountain pens from, as it is hydroscopic and expands with the absorption of water. Fortunately fountain pens sections are never made from Casein so immersion in ink is not a problem. Using a casein fountain pen in a climate with high humidity is another story. Walter A. Sheaffer, in his memoirs, recounts how his firm produced a line of coloured casein pens which proved quite popular until the weather turned hot, whereupon the casein swelled to the point that the sections fell out (it is suspected the swelling had less to do with the heat than with the humidity of a Midwestern summer). The pens had to be exchanged, and Sheaffer states that they were subsequently recycled as loaners – presumably for cool weather use!

The last thing you should ever do with a casein fountain pen is soak it in attempts to remove ink stains or dried ink build-up. Just a few hours in water will be enough to cause the casein to expand by about 10% and will result is the material becoming very soft. If then left to dry out the swelling will shrink but it will almost certainly lose its shape and will be damaged beyond repair. It is reputed that if left in water for long enough a casein fountain pen will disintegrate. I have not yet tried this but the next time I get a broken casein pen I might just try it. Limited quantities of casein plastics are still produced in some countries with large dairy interests, for example New Zealand, and only a few casein fountain pens are manufactured today.

casein inkwell from 1920's

How do I know its casein?
Well there are three ways to find out, one destructive and the other non-destructive. Unfortunately one of the definitive tests is the destructive one! If you want to be certain that it is casein, the soak test will prove it, shame that it has just destroyed your pen!

David Nishimura, well known vintage pen collector and dealer notes :
Destructive testing doesn't mean destroying the entire object.
A tiny scraping may be taken from the inside of the barrel or cap.
Place the scraping on a glass microscope slide, and test it with
solvents. Acetone will dissolve a celluloid scraping. It will not
dissolve casein.
David also notes for technical accuracy "casein" is not capitalized. It is not a trade name. It is a material, like "wood", "water" and "milk".

For the more cautious, try the hand and colour test. Is the pen a Conway Stewart model, highly coloured and has an irregular colourful pattern? If the answer is yes to all these, it could well be casein. Pick the pen up and hold it in your hand. Does it feel warm to the touch? Yes, then the chances are that it is casein. Obviously it may not be highly coloured or not have an irregular pattern, and it may not be a Conway Stewart, but these factors don’t exclude it being casein, they just reduce the chances.

Jonathan Donahaye, prominent Conway Stewart collector comments :
I have frequently noted vintage casein made pens sometimes have a sort of crazy-paving or "craquelé" effect over the surface. This does not seem to occur in other materials and seems to be quite specific for identifying casein. Probably this occurs when the pen has been left for years in the light or perhaps in warm situations where it is affected by frequent moisture changes. This phenomenon is detrimental to the pen quality because the cracks are deep and no amount of abrasives will get them out without damaging the pen. Also the brilliant shine of casein pens is affected by these cracks so that the pattern becomes duller and less attractive. However, many Conway Stewarts from the 30s show no sign of this effect. Perhaps they have been stored away for years in drawers and boxes and so have been spared the ravages of time.

References:
David Wells Vintage Pens
Jonathan Donahaye Conway Stewart Collection
Conway Stewart history
Home of the Plastics Historical Society
Sandretto Plastics Museum Turin, Italy