What a great pen would this one be if I had a cap ...
Why are CS caps so susceptible to this degradation?

It looks that the cap is not a solid piece but a thin layer on top of a substrate that degrades in contact with ink.
The failure typically occurs at the end of the inner cap where ink is collected.
Most probably the inned plastic absorbes the water and through many cycles of wetting and drying it crambles.
You can see it in some pen in its initial state as a grove in the cap. Then in worse cases the cap breaks completely revealing the degraded inner plastic.
Any ideas how to prevent it? Maybe a coating of shellac? Any other ideas?

Awww man! What a pretty pen too.

1. Is that one of the pens they made of casein?

1a. Would a light inner coating of one of the silicone coating compounds form a water barrier without attacking the inner cap material?

2. To salvage this particular pen I guess one could build a gold cap in the shape, salvaging the clip & top and then inscribe the new cap with the barrel pattern.

Antonios,

I think your analysis of the failure mechanism is exactly right. Most people know that casein softens if it gets wet, but it also does need some sort of water content to keep it in good condition. Exposing the pens to excessively hot or dry conditions (not generally a problem in the UK!) does undoubtedly cause deterioration and, as you surmise, cycling does make things worse. I don't think sealing inside will help as the casein does need to breathe. If the inside was sealed, I think you would over time get a build up of water round the sealed area and a resultant swelling.

Do I presume you don't have the broken part of the cap? It is a common problem and a few brilliant people are quite expert in repairing these breaks by using a thin inner reinforcing ring of copper or brass to glue the two halves together and filling the gaps with a suitably coloured resin. If you do have it I can put you in touch with the relevant expert in the UK. The Dandy in this picture suffered the same damage (before it came into my possession).



You don't say what the model number is but it is always possible you will find a replacement cap from somewhere with a little patience. If you let me know what the model is, I'll ask around for you.

Andy

Thanks Andy,

The number is 266. The worst think is that this is a "brilliant" pen as the Brits say The quality of the surface is excellent with almost no surface wear.

The problem with restoring such a patern maybe that the parting line will show up.
In your Dandy the colors blend nicely, but in the cracked ice the repair will be visible. Anyway I will follow up back channel as well.

AZ

PS> THe Esterbrook reliefs have exactly the same problem.

Interesting thread. I don't think all Relief suffer the same problem though, the marbled relief seem to be more stable than the others. At least I haven't seen any with this type of distortion. i wonder if perhaps these were made with a different plastic and not caesin. It seems the "funkier" plastics all suffer. I have my fair share, unfortunately.

Nice pics AZ, thanks for the closeup!

Best-
Brian

Brian here they are. The 3-L and the 5-L in the middle. Also note the black 3-L on the right which is at the early stage of the process. The closeup shows exactly the same pattent of deterioration.

Ugghhh. I'll have to check mine when I get back from work. Perhaps I'm in denial.

Oh, and that relief pencil looks like it is going to deteriorate too, perhaps you should send that to the relief hospital here in nice cold Wisconsin for some, er.., relief.

Forgot you had that pencil. Very uncommon, I think I've only seen two of them in my years of collecting.

Best-
Brian

Right...... now I know why it's happening.

I've got a blue marbled 2-S thats gone exactly the same way. Funny thing is I've done the same as in the picture and teamed it with a black cap in a Pelikan fashion.

And I was recently offered a 228 cracked ice well one it's way to the same state which I turned down.

Brian,

I believe the CS pre-war marble materials were mostly (if not all) casein, while after the war there was a move to celluloid for the marble materials, so that the CS 27, 28, 58, 60 series marbled pens (from the 1950s) for instance are celluloid.

I'm sure there will be no shortage of people to advise me differently if I am wrong but I think this probably explains the differences you have noted in ageing characteristics.

Andy