Silicone vs rubber sacs?

[spaceink]

If one finds a celluloid pen that's not from one of the aforementioned large penmakers, is there a way to know that a silicone sac should be used?

[mhosea]

I'm not sure how to interpret "should" in such a broad context. I use the pure silicone sacs (vintagepens.com) in collection pens that have good color presentation but which are vulnerable to ambering. I would know that by observing what various other samples of that material look like now. If it's vulnerable, many will be obviously discolored. Obviously an opaque black celluloid pen can take a latex sac. A well-preserved jade celluloid pen deserves a pure silicone sac, IMHO.

 

Having said that, I don't like silicone sacs for daily use because of the gas permeability issue. I like them fine for "fill it and use it for one day, then empty it, clean it, and return it to the collection" use. If not to be used at all, a collection pen wouldn't need a sac of any kind, obviously.

 

My understanding is that PVC "silicone" sacs should not be used in celluloid pens, though I wonder how many celluloid pens they actually have been used on during the time when people thought they were pure silicone.

[spaceink]

Thanks for your input. Looking at other examples is a smart way to see if silicone might be worthwhile.

 

My silicone sacs have come from Anderson Pens, who says theirs is pure, so I'm trusting them on that.

 

I've been using an ebonized pearl Sheaffer with one inside for the past week and haven't had a drying problem. Not sure what others' experience has been like, but seems like it's working for me?

[mhosea]

I've been using an ebonized pearl Sheaffer with one inside for the past week and haven't had a drying problem. Not sure what others' experience has been like, but seems like it's working for me?

 

It's not a drying problem, rather that the feed floods eventually because air slowly gets into the sac through the sac instead of as air bubbles from the feed while writing. If you use the ink up fast enough, you might not notice, but for this reason it is recommended to store the pen upright if it has a silicone sac and is inked. This helps but isn't a cure.

[fireskink]

A slight side note: another small advantage I can imagine for the user re "silicone" sacs over latex, hinted at above - those of us with allergies to latex! (Obviously vintage fountain pens were the *ideal* field to get involved with having this... - though better than my nurse yesterday who told me she was one of nine children 'because of her father's latex allergy' !!). Personally I use nitrile gloves when handling latex sacs, though it does mean I don't have the same degree of fingertip sensitivity that I would like, but I can imagine that if a company could develop a better alternative to the "silicone" sacs that were suitable for use in lever etc fill pens, it would be a blessing to those of us who struggle with handling latex, and would allow people with more severe problems with it to get involved with restoration etc. I hope someone down the line will manage to develop a sac that has that advantage with all the other indubitable advantages of latex sacs!

[spaceink]

Thanks for the clarification, Mike. That likely explain some random wet nibs in the past with my ebonized pen.

[Ron Z]

This article on my blog goes into some detail about the different sac materials and the issues that they have. None are perfect, some better than others. As Mike pointed out, the true silicone sacs have gas permeability issues that can cause a pen to flood. Not all pens, not all the time, but often enough that I decided that they were not appropriate for use in clients pens. You also have to use silicone cement to secure the sac. You use shellac for latex and the PVC sacs, but silicone only sticks with silicone cement.

[pajaro]

This article on my blog goes into some detail about the different sac materials and the issues that they have. None are perfect, some better than others. As Mike pointed out, the true silicone sacs have gas permeability issues that can cause a pen to flood. Not all pens, not all the time, but often enough that I decided that they were not appropriate for use in clients pens. You also have to use silicone cement to secure the sac. You use shellac for latex and the PVC sacs, but silicone only sticks with silicone cement.

 

I red most of the blog, and where you discuss the PVC sacs in Parker 51 aerometric pens causing the sac nipples to soften and tear because of the plasticizer leaching out of the PVC sacs. I accept what you say, but I have never had this happen with any of my pens, and I have several from 1948 and 1949. Why haven't these pens failed? How long does it take for the softening of the sac nipple to take place, and would it help to replace the PVC sacs with new sacs? Should I use latex? PVC?

[mhosea]

but I have never had this happen with any of my pens, and I have several from 1948 and 1949. Why haven't these pens failed?

 

My understanding is that the first aerometrics had acrylic connectors. The ones that soften were immediately after that.

[Ron Z]

I red most of the blog, and where you discuss the PVC sacs in Parker 51 aerometric pens causing the sac nipples to soften and tear because of the plasticizer leaching out of the PVC sacs. I accept what you say, but I have never had this happen with any of my pens, and I have several from 1948 and 1949. Why haven't these pens failed? How long does it take for the softening of the sac nipple to take place, and would it help to replace the PVC sacs with new sacs? Should I use latex? PVC?

It is by no means universal, though neither is it uncommon. It's possible that either the plastic of the connector, or the formulation of the sac itself was altered at some point. David Nishimura may disagree, but I think that the adhesive may play a role too. I use the PVC sacs because in this case I think that they are the better option.. There is a layer of shellac between the sac and the sac nipple, so it does not come in direct contact, which we think is necessary for the softening to occur.

[pajaro]

It is by no means universal, though neither is it uncommon. It's possible that either the plastic of the connector, or the formulation of the sac itself was altered at some point. David Nishimura may disagree, but I think that the adhesive may play a role too. I use the PVC sacs because in this case I think that they are the better option.. There is a layer of shellac between the sac and the sac nipple, so it does not come in direct contact, which we think is necessary for the softening to occur.

 

Thanks for this insightful reply. I did have to wonder if, after the passage of the decades since the pens were made, if the PVC might have been slowly acting on the sac nipple, but the reasoning that the shellac protects the sac nipple is a great explanation. It sets my mind at rest, because I am sure Parker would have assembled the pens using best practices of the time, shellac as an adhesive for the sac. Thanks again.

Edited September 29, 2015 by pajaro

[spaceink]

Would a makeshift soluton for using silicone sacs (and thus minimize further discoloration) be to remember to under-fill the pens installed with them?

 

I wouldn't mind filling ink more often if it means I can aesthetically preserve the pen's celluloid.

[mhosea]

Would a makeshift soluton for using silicone sacs (and thus minimize further discoloration) be to remember to under-fill the pens installed with them?

 

I would think, rather, that one might try keeping them as completely full as possible because, and I'm just spitballing here, air is probably going to migrate into the sac where there isn't ink on the other side, due to slightly lower ambient air pressure inside the sac (incompletely equalized by air-ink-interchange while writing).

Edited September 29, 2015 by mhosea

[spaceink]

Yes, keeping them full makes sense then.

 

Hmmm...then maybe to coat the sac with a layer of something like nail acrylic (if that doesn't have sulfur compounds) to reduce the permeability factor? Trying to brainstorm a solution.

Edited September 29, 2015 by spaceink

[Ron Z]

Nail acrylic as you call it, has solvents that will continue to come out of the material for some time after you put it on. It could damage the plastic (using the generic term) of the barrel. It also hardens, so would likely either make the sac too stiff, or would flake off as you flex the sac to fill the pen.