When replacing an old latex rubber sac in a pen with a newer silicone version, what is the preferred adhesive? Can I still use shellac, or do I need to source a new adhesive liquid?
When replacing an old latex rubber sac in a pen with a newer silicone version, what is the preferred adhesive? Can I still use shellac, or do I need to source a new adhesive liquid?
"When Men differ in Opinion, both Sides ought equally to have the Advantage of being heard by the Publick;
and that when Truth and Error have fair Play, the former is always an overmatch for the latter."
~ Benjamin Franklin
RTV is necessary Jon. Silicone adhesive or sealant. Shellac won't stick to the silicone.
bugsydog55 (November 14th, 2020)
"When Men differ in Opinion, both Sides ought equally to have the Advantage of being heard by the Publick;
and that when Truth and Error have fair Play, the former is always an overmatch for the latter."
~ Benjamin Franklin
Get the big tube...
"When Men differ in Opinion, both Sides ought equally to have the Advantage of being heard by the Publick;
and that when Truth and Error have fair Play, the former is always an overmatch for the latter."
~ Benjamin Franklin
Jon Szanto (October 1st, 2020)
I had to dig into this when the silicone sacs came out. There's a thread on the "other" board where I discussed this in some detail. You might want to look for it, because it gets into the different types of RTV silicone made. You do need to use a silicone adhesive because nothing else will stick. A non-corrosive version would be best. I think that my post in the thread gives specific product information. I'd have to dig again to get the information right here.... Maybe I need to look for the thread too, and do a blog post.
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da vinci (October 1st, 2020), Dreck (October 2nd, 2020), Jon Szanto (October 1st, 2020)
da vinci (October 1st, 2020), Dreck (October 2nd, 2020), Jon Szanto (October 1st, 2020), Nethermark (October 2nd, 2020)
Thanks Fred. For those who haven't looked for the thread, here is what I posted:
I had to go back and look at my notes. Its been 5 1/2 years since I looked into this, and in the interval I quit using the silicone sacs because of the gas permeability issues, so the silicone I had expired long ago and got tossed.
The common RTV is an acetoxy compound, and releases acetic acid when curing. This is why it is considered to be a corrosive RTV. That isn't the issue with pens, but the release of acetic acid around celluloid could be, so it may be good to avoid it, or leave it open to air until it cures - roughly 24 hours.
So I went looking for a good non-corrosive RTV, and had a long conversation with the folks at Loctite. There are other forms of RTV curing materials, but the one recommended is an Alcoxy RTV. This releases alcohols - mostly a combination of methyl and ethyl alcohol. Loctite makes one called 5040 self leveling RTV. It's a bit pricey though, and you'll need to order it. I found it at a number of sites, including Amazon.
Another possibility is Loctite 598, which is an oxime cure RTV, and is much cheaper than the 5040. You can find it on ebay. This releases methyl-methyl keytones, but the quantity would be rather small in this application.
If you're not sure about what a product releases, take a look at the technical data sheets. There's a wealth of information for those who take the time to dig for it.
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da vinci (October 1st, 2020)
Well done, Fred - I looked but failed to find. Although I did find one from April last year where Ron said:
You can't fault the consistency.There's a thread somewhere on FPN where I go into detail on this. I should do a blog post so I can refer to it.
In the words of Paul Simon, you can call me Al.
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Thanks all for the information. The whole conundrum of whether to go silicone sac or not is such a pain, given that it isn't a methodology without issues itself. I've not had to deal with this much, in that any of the pens that I specifically wanted to keep from any off-gassing issues were - at least at this point in my life - ok to be without sacs at all.
I'll do some research/shopping for the most benign but effective adhesive and certainly keep it all well away from other pens.
"When Men differ in Opinion, both Sides ought equally to have the Advantage of being heard by the Publick;
and that when Truth and Error have fair Play, the former is always an overmatch for the latter."
~ Benjamin Franklin
Jon Szanto (October 1st, 2020)
FWIW, you will have to use a silicone adhesive. Nothing else will stick. IIRC the tech support at Loctite confirmed that. Even then it isn't a super strong bond.
My opinion? A silicone sac isn't worth the effort. I still have a bunch, and will install one if asked, but the gas permeability is an issue. "Just store the pen nib up and you'll be fine." I don't store my pens nib up, and I can't tell customers to store their pens nib up. Instead I'm likely to have a re-do because they don't like the oozing - even if they asked for a silicone sac. I took them out of my pens.
Peter Amis says that the formulation of the rubber used in modern sacs is such that there shouldn't be a discoloration problem. I can't argue one way or the other. There are no silver bullets.
Last edited by Ron Z; October 1st, 2020 at 01:04 PM.
Visit Main Street Pens
A full service pen shop providing professional, thoughtful pen repair....
Please contact us by email, and not PM for repair inquiries.
Dreck (October 2nd, 2020), Jon Szanto (October 1st, 2020), Ole Juul (October 1st, 2020)
Dreck (October 2nd, 2020), Jon Szanto (October 1st, 2020)
Bert Heiserman once said the same thing to me about the modern latex sacs. I don't have any proof in either direction.
The silicone sacs are a pain from my standpoint because even if the pen is stored nib up, the ink blobs out into the cap. I've shaken the pens, tried to get all the ink to drain down, etc. It still has ink in the cap when I come back the next morning. The only thing that did seem to work was totally draining the nib and feed using a paper towel. Even then, if I missed any ink, it appeared in the cap the next morning. I own maybe 2 nice jade Sheaffers and one black/pearl Sheaffer. The rest of my pens should be fine with latex.
Last edited by Ray-VIgo; October 2nd, 2020 at 08:12 AM.
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