Silicone sacs
#1
Posted 11 January 2013 - 04:53 PM
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
#3
Posted 11 January 2013 - 11:56 PM
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).
#5
Posted 12 January 2013 - 06:05 PM
#6
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
#10
Posted 14 January 2013 - 11:04 PM
Latex rubber sacs are fine in HR pens and in celluloid pens that aren't so prone to discoloration.
#11
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
June's Antique Deskstuff
#13
Posted 16 January 2013 - 09:37 PM
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.
#15
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
Posted 17 January 2013 - 11:52 PM
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
#18
Posted 18 January 2013 - 02:42 AM
Hmmm might have to order some of these as well.
#20
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 .....
TERI
TERI MORRIS
www.peytonstreetpens.com
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