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Silicone sacs


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#1 David Nishimura

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Posted 11 January 2013 - 04:53 PM

Some good news and some bad news.
The good news is that Mark Hoover and I are now producing injection-molded silicone rubber pen sacs. Great material, lasts forever, doesn't take a set, won't discolor celluloid, won't turn to goo with fancy inks, yada yada yada.
The bad news is that in getting into this project, we found out that the "silicone" sacs that have been on the market for the past several years really aren't. Instead, they are PVC -- a material that is not nearly as non-reactive as silicone (PVC has been known to attack other plastics when left in direct contact for an extended time). This was a real shock to both of us, as I'm sure it will be to the many collectors who have likewise been deceived.

I've just posted a video that demonstrates how you can tell real silicone from fake:

Silicone pen sacs: identification and testing

#2 FarmBoy

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Posted 11 January 2013 - 06:20 PM

As David mentions, the samples of old 'silicon' sacs I have are indeed PVC that is heavily plasticized. I'll try to scan some spectra of the sacs I have and a reference PVC sample for fun.

Todd

#3 David Nishimura

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Posted 11 January 2013 - 11:56 PM

Thanks for the analysis, Todd!
By the way, if anyone wants to repeat the comparison testing shown in the video, I've got plenty of silicone tubing scraps that I'm happy to send out to anyone who sends me a self-addressed stamped envelope (or you can pick some up from me at the LA show).

#4 Ken W

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Posted 12 January 2013 - 03:30 PM

Thanks for this information. It turns out that the "silicone" sacs that I purchased a few years ago are indeed PVC. Are the PVC sacs safe to use in hard rubber pens, or should I just toss them?

#5 LedZepGirl

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Posted 12 January 2013 - 06:05 PM

This is good to know! I'm all to familiar with what PVC can do to other plastics. When I was a kid I had inflatable Barbie doll furniture that happened to be stored with hard plastic items when I was done playing with dolls and sat that way for years. Earlier this summer I get this stuff out of storage so I can pass it along to my cousin's five year old daughter and the items that were in contact with the vinyl furniture were melted, covered in melt marks and pretty much destroyed. Thankfully it was only cheap plastic toys.
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#6 David Nishimura

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Posted 12 January 2013 - 07:11 PM

Thanks for this information. It turns out that the "silicone" sacs that I purchased a few years ago are indeed PVC. Are the PVC sacs safe to use in hard rubber pens, or should I just toss them?


PVC should be OK in a hard rubber pen.

It's the plasticizer in the PVC that does the damage, and it's known to wreak havoc with cellulosics and styrenes. Judging from the lack of observed plasticizer damage to early Aerometric sac nipples, acrylic is not vulnerable. I'd not put a PVC sac in a Waterman Hundred Year Pen, though, since (little known fact) the transparent colored ones have a coat of tinted lacquer inside which would be highly vulnerable to PVC plasticizer.

Another data point for PVC damage to pens would be older display cases with padded vinyl linings, such as the blue Waterman Etalon cases from the 1980s. I had a couple of these cases and the top pads had begun to stick to the pens inside. I caught it right away and there was no lasting damage, but it took some work to get the residue off the surface of the hard rubber and overlay pens. I stripped out the linings and replaced them with cotton velveteen. I've head of other instances where celluloid pens were involved and the damage went deeper.

David

#7 June H

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Posted 13 January 2013 - 08:27 PM

David :

Where does Laytex sacs fit into this. Are they good, bad, or what?



June

#8 LedZepGirl

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Posted 13 January 2013 - 09:56 PM

David :

Where does Laytex sacs fit into this. Are they good, bad, or what?



June


They aren't good for brightly colored celluloid pens- like jade green Duofolds, ect, and will cause discoloration if they haven't already.
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#9 June H

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Posted 14 January 2013 - 04:46 PM

Should you just turf the latex then or use them in hard rubber also?.

June

#10 David Nishimura

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Posted 14 January 2013 - 11:04 PM

We'll all still be using latex for a while yet. There's no alternative available yet, for example, for special-purpose sacs like those for Vacs and Ink-Vues. And injection-molding gets very tricky when you get to long, thin, thin-walled sacs.

Latex rubber sacs are fine in HR pens and in celluloid pens that aren't so prone to discoloration.



#11 June H

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Posted 15 January 2013 - 06:15 PM

We'll all still be using latex for a while yet. There's no alternative available yet, for example, for special-purpose sacs like those for Vacs and Ink-Vues. And injection-molding gets very tricky when you get to long, thin, thin-walled sacs.

Latex rubber sacs are fine in HR pens and in celluloid pens that aren't so prone to discoloration.




thanks to Ledzepgirl and David Nishamura for the help on laytex and the very informative update on silicon sacs.
June

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#12 John Jenkins

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Posted 16 January 2013 - 08:32 PM

Great news for the hobby. Thanks for investing the time!

I just bought a hundred for myself and the Dallas Pen Club.

John
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#13 Brian Gray

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Posted 16 January 2013 - 09:37 PM

I'll vouch for these sacs.

I'm using them in my pneumatic fillers and all of my bulb fillers will be switched over to the silicone.

I'm very happy with them.

#14 LedZepGirl

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Posted 17 January 2013 - 06:47 PM

Just wondering, do they come small enough to fit a Peter Pan pen? In the next few weeks I need to get a sac for one and I'm going to replace the sacs in all my Duofolds, and Doric which have the old silicone (vinyl sacs).
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#15 Brian Gray

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Posted 17 January 2013 - 08:16 PM

Just wondering, do they come small enough to fit a Peter Pan pen? In the next few weeks I need to get a sac for one and I'm going to replace the sacs in all my Duofolds, and Doric which have the old silicone (vinyl sacs).


They are only #18 right now. My understanding is the David is working on other sizes.




#16 David Nishimura

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Posted 17 January 2013 - 11:52 PM

Brian is correct. We should have #14 and #16 sacs available within a month or three, and after that we'll see where to go next.
We will not be going any smaller than #14 anytime soon though. Demand for tiny sacs is low and they are very difficult to injection mold that small and that thin.

David

#17 Procyon

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Posted 18 January 2013 - 12:48 AM

David,

I would vote for #20 - I seem to use a lot in that size.

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#18 Earthdawn

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Posted 18 January 2013 - 02:42 AM

Man .. I just ordered some 18's to try and do a little conversion on my kaweko sport..

Hmmm might have to order some of these as well.

#19 LedZepGirl

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Posted 19 January 2013 - 09:41 PM

I was thinking about this the other night, but couldn't pen sacs be made from TPE also? Like silicone, feels a lot like it and it's used in medical implants and can be moulded.
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#20 Terim

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Posted 12 July 2013 - 09:19 PM

Brian is correct. We should have #14 and #16 sacs available within a month or three, and after that we'll see where to go next.
We will not be going any smaller than #14 anytime soon though. Demand for tiny sacs is low and they are very difficult to injection mold that small and that thin.

David



Any update on other sizes for these sacs? David's web site only shows the #18 .....


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