Rubber Or Silicone Sac For 'bulb Filler' Bodge?

[PDW]

I've just received in the post a Brazilian Pilot 77. The tip of the lever on the filler actuator is broken off so I'll keep the sac guard/pressure bar assembly, but I've no great desire to replace the lever at present. So it looks like it's going to have to be a bulb filler when I've replaced the sac.

 

Given that the sac is going to be handled directly at each refill, which is better for maximum longevity - rubber or silicone? Or doesn't it matter?

[Ayami_109]

Silicone is less likely to interact with certain inks and melt, unlike rubber. Say if you had some ink residue left in the sac and you filled the pen with another ink but both inks reacted together in an undesirable manner, the rubber sac might melt. As for the question of longevity pertaining direct handling, I don't think it really matters. That's just my 2cents.

Edited October 30, 2014 by Ayami_109

[pen lady]

I have read that you can't use shellac to attach "real" silicone sacs, some other kind of adhesive is needed (silicone caulking????). A latex sac can be attached with shellac in the usual way. The Eversharp Bantam bulb fillers that I've repaired had a metal crimp ring round the sac and nipple originally too.

[Ron Z]

Latex sacs and PVC sacs ("silicone" sacs from Woodbin) can be attached with shellac. Clean out the inside of the PVC sacs with alcohol to remove any residual mold release compound. The silicone sacs from David Nishimura (aka Vintage Pens) need to be secured with silicone cement. If you leave it out to cure, you can use a standard non-corrosive RTV silicone adhesive.

[PDW]

Thanks all, but I need to frame my question more clearly. It's the long-term effects of repeated skin (with oils, debris, dandruff ...) contact directly on the sac that I'm curious about. Most sacs, hidden in sections and operated on by metal gizmos of various designs, don't have to put up with this, but a bulb filler's sac does.

 

So, any thoughts?

[mhosea]

Pure silicone sacs are more chemically robust but they tear more easily. Name your poison.

 

http://www.vintagepens.com/FAQrepair/pen_sacs.shtml

 

I'd be interested in knowing what experiences have led the repairers not to recommend shellac with the pure silicone sacs. I started out using RTV, but when I experienced gas permeability problems on the one hand and wettability issues on the other (same problem as seen in some converters only much worse), I switched several of my user pens back to latex. Since then I have also, in the course of random repair events, removed slicone sacs attached with shellac as well and not noted much of a difference in adhesion. I suppose it's the touchdown fillers that I'd be most concerned about, as pulling the touchdown tube out tugs on the sac a little. I solved the wettability problem, BTW, by installing the sacs with a 1.5mm wide thin strip of polyethylene plastic that I also roughed up a bit with the pink side of a buff stick. It takes a few seconds for gravity to win, but the ink can't seem to stay put with the strip passing through it.

[Ron Z]

The answer is simple. Nothing sticks to silicone but silicone. Silicone RTV will stick to both the sac and the sac nipple.

 

All three of the materials used for sacs have their unique advantages and issues. You might find this blog post to be useful. With the work going on before our move, the move earlier this year and catching up I haven't had a chance to write any more posts on the blog since then, but nothing in my experience doing repairs has changed my perspective. For general repair of vintage pens, I still prefer latex. For snorkels and touchdowns where the PVC sac coming in contact with the plastic because of the sac guards I use PVC exclusively. I like the concept of silicone, but the permeability and adhesive issues keep me from using them very often.

[mhosea]

Do you use the Woodbin "Thin Wall Clear Silicone Sacs" or the "Soft Clear Silicone Sacs" on the Snorkels? I realize that it says that the thin-walled ones are for Snorkels and such, but with latex we don't worry about the thin-walled business.

Edited October 31, 2014 by mhosea

[zchen]

Do you use the Woodbin "Thin Wall Clear Silicone Sacs" or the "Soft Clear Silicone Sacs" on the Snorkels? I realize that it says that the thin-walled ones are for Snorkels and such, but with latex we don't worry about the thin-walled business.

 

that was going to be my question too since woodbin doesn't have the 14 1/2, 15 1/2, and 17 1/2 size in non thin walled versions when I asked him. Does that mean I can use the 16 and 18 pvc for tm touchdown and fat touchdown/tuckaway?

 

Also, to prevent discoloration in pens like the Sheaffer Flat Top in Jade, true silicone sac is still the best right?

Edited October 31, 2014 by zchen

[pen lady]

I've been using Woodbin's "silicone" sacs, that I understand are actually PVC, in pens that react badly to latex for years with not apparent ill effects. They can be attached with shellac whereas true silicone sacs will only stick with special silicone adhesive. Amazing what a person can learn from reading Ron Zorn's postings - thanks Ron

[PDW]

Pure silicone sacs are more chemically robust but they tear more easily. Name your poison.

 

http://www.vintagepens.com/FAQrepair/pen_sacs.shtml

 

 

 

From the article (thanks for the link!) it seems that some non-rubber sacs can damage pens in uses like mine where there would be direct contact between sac and barrel.

 

I think I'll use a latex sac and replace it if/when needed - it's easier than finding a replacement for a softened barrel

Edited November 2, 2014 by PDW

[mhosea]

I think I'll use a latex sac and replace it if/when needed - it's easier than finding a replacement for a softened barrel

 

This is the approach I take with most of my "user" pens. The collection pens get pure silicone when it is called for.