Montblanc casein stars
how to fit them into ebonite cap tops.
Here is a story, that started long time ago, when I had to restore a restore a MINT 136 pistonfiller.
Just the Casein star needed to be pushed back into the hard rubber cap top.
It won´t enter fully - so I decided to heat the hard rubber a tiny bit - hoping the softened ebonite would expand a little and allow the
star to enter. What happened then almost made me faint: The star shaped opening of the hard rubber top slowly became an even round hole!
I then realized - these casein stars had been pushed into a round hole and then, after heating the hard rubber the softened material was shrunk around the star.
I made a trial - did such a process on a stick of ebonite - yes, it works.
Now, long time after this "learning by killing a cap top" I found the patent relating to this.
Here is another cap top without star, which I heated - and you see, the hole once again turned from star shape into round shape.
Look at the original 134 star, which I had to restore.
One mistake in the original way of production technique was, that the casein is in constant contact with ink.
And ink = water makes Casein grow/expand in size. This makes the star move to the outside.
And ink discolors the casein, as it seeps out between casein and hard rubber.
Something, that is most likely to happen, when shipping a pen.
Nicely cleaned and polished before shipment, but some water left?
The water will move outside - dissolve the ink hidden at the side of the star -
and 1. discolor the star and 2. make it expand and come out of the cap top.
Here you see such a cap top after it returned for repair.
I now knocked out the star, cleaned the star - in water and cleaner.
It sure is expanded now for the water it soaked, so I leave it for a day to dry so it becomes smaller again.
I then glue the star back into the ebonite - and make sure, it is shut against the ink with a plug of resin from the inside.
Not too much, the nib might hit the ebonite plug.
After this operation, the star will be polished to perfect, smooth, white, no step between black and white.
And no ink coming out again. And no star coming out again. :-)
Below, you see the drawing - this is from the Montblanc patent, showing how they fixed the star in production -
1. drill a hole ( a round hole)
2. fit the star into the hole.
3. heat the rubber - so its it soft
4. Press the rubber around the star.
5. now the star is permanently fixed, in a manner, that it won´t get out even if working on the lathe or mill.
6. Thus, the final product is made AFTER fixing the star in the raw ebonite.