calling all materials science peeps:
what are the physical differences b/t cellulose acetate and cellulose nitrate? i know both are made of cellulose (wood pulp), and that cellulose nitrate requires camphor in the manufacturing process, requires aging for stability, is flammable (like film stock), and is what ping pong balls are made of.
can both be accurately called celluloid? which pens are made of cellulose acetate and of cellulose nitrate?
is cellulose nitrate inherently superior? apologies if this has been discussed previously (i searched the forum archives).
Generally, both materials are called celluloid, although that is not entirely correct. Cellulose nitrate is the stuff that was used for film in the past, which is why in cinemas they had fires every now and then, or broken films, if the film got too hot in one spot and burnt through or got weaker.
Cellulose acetate is the safe variant of this material, and I don't honestly know whether this was used in the film industry.
Celluloid, especially the marbled varieties used for pens, has an incredible depth to it, which I have never seen captured properly in pictures. Also, it is a little dangerous when turned: you shouldn't let it get too hot when making a pen out of it. It is also very tough material, very difficult to break, and usually has a faint camphor smell, as you indicated. Because it is so tough and difficult to break, shapes can be turned that are very thin walled, giving it an additional translucency.
Disadvantage is that it may get stained by ink, and that it doesn't like prolonged stays in or contact with water. This is why piston fillers made of this material generally have some kind of internal sleeve to protect it from ink, or have rubber sacs (like early/vintage celluloid pens).
Cellulose actetate, by some manufacturers called "Cellocride", is very similar to celluloid, but is not flammable. It is slightly more brittle, and thus breaks a little more easily, but it can stand heat and water a little better than celluloid. It has nearly the same depth that celluloid has, but not completely the same.
Oh, I think, but I may wel be wrong here, that it is only a fairly recent development that resin actually achieves similar transparant qualities, without it looking cheap, and without smelling strongly of glue or burnt plastic. Even so, the depth of celluloid is IMO second to none.
As you may know, I have a few Stipla Etrurias in my collection, and some of the models are made from true celluloid, and some from "Cellocride", and others from resin. I think the resin ones come fairly close to translucency and depth to the cellulose acetate variants (the non-black ones
), but I reckon the celluloid ones are in a class by itself. Of course, this is all in the eye of the beholder, in this case me
Interesting in this regard is the Etruria Amber, which comes in a the new version nowadays, made in cellulose acetate, and with a big piston converter, and in an older version, if you can still get your hands on one, the Etruria Amber Grande, which is a piston filler made from real celluloid. IMO, it looks better. There is more depth to the red and amber marbling in the brown substrate of the pen. Oh, and it has a sleeve around its filling mechanism, to prevent ink coming into contact with the barrel.
HTH, warm regards, Wim