Cork Compressibility

[FountainNewbie]

Hi guys!,

 

so I'm lately into collecting some soennecken and The Tower. They are extremely well built and very solid, I only wish they could come with a collar rather than friction fit ...

 

Anyway, I'm writing here because I would like some opinions about corks...

 

I've tried fitting cork to some of the pens with very little success. For some, I've resolve to put o-ring but the look is not the same. So I've retaken the challenge of installing cork on them.

 

I cut the cork and sand them manually (very painstaking). 90% of the times the cork is not symmetrical so there is some type of leakage. I don't wax the cork, only apply silicone grease after sanding.

 

I think the main problem might be the cork I use. I've read 'flor cork' is the best quality, but I was thinking what type of cork has the highest compressibility?. So far, I've used 'agglomerate' cork of different 'particle size'.

 

https://www.fountainpennetwork.com/forum/topic/330756-source-for-piston-cork/?hl=flor&do=findComment&comment=3967866

https://www.fountainpennetwork.com/forum/topic/291655-cork-for-pistons/?hl=flor&do=findComment&comment=3375623

 

That is, I think a solution to my problem would be to find a more 'spongy' cork that could accomodate irregularities in the barrel and asymmetry from sanding the cork manually. The last one I used was agglomerate with very fine particles, I thought was going to be better quality but then realised it was too hard (when pressing with the fingers it barely compressed).

 

I've tried to find any compressibility data on cork grades without success. Maybe anybody in here has a tip?, any way I could 'soften' the cork and make it more spongy?

 

Thanks a lot for any advice in here, hopefully I can give some insight if succeeding

 

 

[siamackz]

I am glad you are using cork in those piston fillers, as was originally done. I find the process painstaking too as I dont have cutters designed to speed up the process. With practice though, you will become more skilled of course. I use flor cork too. I believe it is sufficiently forgiving in terms of compressability. I would recommend that you bathe it au Bain Marie in a solution of beeswax and paraffin oil (might be called something else where you are). I learned this from Fountainbel. Maybe just beeswax will work too? This seals any pits that might occur naturally in the cork. Then silicone.

 

All the best.

[christof]

Making cork seals without proper tools is indeed difficult. In my opinion, you will need at least a power drill and a proper cutting tool....and of course a solid block of premium cork.

 

I wrote about how I proceed a while back on this forum. Here's an illustrated guide for a Pelikan 100 for example:

 

Pelikan 100 gets new cork seal von -c_m_z-

 

recently I bought the cutting tool by Tom Westerich and got some solid cork from Portugal:

 

Kork von -c_m_z-

 

C.

Edited July 10, 2019 by christof

[siamackz]

Excellent set up, and fantastic photo tutorial. I literally cut the cork with an Xacto knife and then hand sand 🤦‍♂️

[christof]

Thank you.

 

I think the mayor problem with sanding by hand is to geht a straight sealing surface . A curved seal surface can produce a vacuum, but is often not ink tight in long term use...

 

Cork Piston Seal by c_m_z, auf Flickr

 

C.

[siamackz]

Thank you.

 

I think the mayor problem with sanding by hand is to geht a straight sealing surface . A curved seal surface can produce a vacuum, but is often not ink tight in long term use...

 

Cork Piston Seal by c_m_z, auf Flickr

 

C.

Precisely! Ive ordered for a dremel, its long over due. I hope I come up with a creative solution using that tool.

[FountainNewbie]

Wow!

 

Thanks a lot guys, this really helps and got some ideas how to proceed now.

 

I found those cork from Portugal Christof mentioned (from ebay), they have several options and I just bought the 'cork stoppers' of 1/2 inch diameter (1,27mm). I think this ones will be the easier to sand down to about 8-9mm. They seem to be flor cork. They already have a similar shape to what I need.

There are also stoppers of 0.75 inch (1,9mm) diameter, but I think it would be a lot of work to sand down to the proper diameter.

 

Previously, I was cutting with an Xacto and then sanding down with a file (like Siamackz). Because I didn't have the proper tools, I had to sand down a lot to give it a proper shape, I think in the process I got an uneven diameter and the problem Christof displayed on his drawings.

Also, I think the cork I was using had a lot of glue to put particles together. I think this glue provides some 'leakage path' if sanded.

 

The only it time it worked for me was with an old Pelikan 100 (like Christof), but the plug at the end is missing. So I had to carve the cork inside to cover where the plug is supposed to be. It's not the most elegant but it worked. Doesn't have leakage so far (see pic).

 

Siamackz, I was also thinking about sanding down with a dremel (if the dremel is mounted and with a sanding with a block as Christof mentioned), just need to keep in mind that a dremel has a very high speed so the sand paper has to be not so rough. There is an accessory to mount the dremel vertically.

 

Thanks again guys, I have to think a bit how to do about the dremel/sanding process. To make it stable and perpendicular to the sanding block

 

 

 

 

 

 

 

 

[FountainNewbie]

just received the corks from Portugal (no affiliation)... they are top quality!, 1.2cm diameter very well cut

[FountainNewbie]

I made a small device to sand the cork from the plugs above to the right diameter. Hopefully it helps other people on a budget or that will cork the pens seldom. The device allows sanding both diameter and making the top/bottom of the cork straight. In the pic I'm making the top flat.

 

The lego pieces allows moving parallel or perpendicular.

[fountainbel]

just received the corks from Portugal (no affiliation)... they are top quality!, 1.2cm diameter very well cut

 

Nice clean cut corks !

But unfortunately the cork should be cut square to the center of the tree, and not parallel to the thickness of the bark as yours are.

You can clearly see the lengthwise grooves in most of your corks, and these will lead to leakage.

By cutting square your will not have these grooves but only little holes/cavities which can be filled up with beeswax/ grease.

And even then In practice when I cut corks I can only 3 to 4 corks out of 10, because of natural defects in the cork.

Mounted on its seat, the external cork diameter should be 0.15-0.20mm larger as the barrel bore.

The way Christoph cuts his natural corks is the perfect approach

On the attached sketch you can see what I mean.

Hope this helps

Francis

 

 

[kdv]

Ls,

Most piston shafts won’t fit into a Dremel: shaft is to broad/fat.

So, I first (after cutting the right length of the cork) put the cork on a small/diameter bolt and secure it in its place with nuts and then secure this on a Dremel for sanding the outside diameter of the cork.

Next step (for me) is – in steps - drilling the right inside diameter.

30 percent first time luck till now.

 

Greetings

kdv.

Edited August 18, 2019 by kdv

[christof]

The way Christoph cuts is natural corks is the perfect approach

 

Thank you Francis....but I am just proceeding exactly how you learned me to do.

c.

Edited August 18, 2019 by christof