"Faraday Wax" - recreating old school high-vacuum epoxy!  - Page 1
Forum section: electronics / general

author: ChristofferB
author_rank: Frequent Contributor
timestamp: May 23, 2021, 10:23:56 pm
content: Hi! I've posted about this on some other forums but I thought you guys might be interested as well!I'm doing a lot of high vacuum stuff, and this gets expensive fast, if one were to do things by the book. The standard high vacuum epoxy, Torr Seal (by Varian) is very expensive, and the generic high vacuum epoxy, Hysol 1C is not available in EU.EDIT: I got around to making a quick video on how to use the wax for sealing purposes, I hope it's OK I attach it here:Apparantly, in the olden days, a red wax was used to seal vacuum systems, make glass-to-metal seals etc. well into the 20th century. A famous example is Lawrence's first 4-inch cyclotron in 1930:I found a recipe in a review from 1936 (L. Walden, J. sci. instrum. 13, 345) that describes "Faraday wax" - as first described by Michael Faraday in "Chemical Manipulation" from 1827.By weight:1 pt. yellow beeswax5 pt. colophony (Rosin)1 pt. Venetian redMelt beeswax, add rosin gradually, add Venetian red and stir until uniform, stir while cooling. I poured mine into strips on baking paper to be touched to the preheated surfaces to be joined. Can also be applied with brush if used directly from the melting pot. Mine melted nicely around 130-140*CI sealed a KF25 flange with a 10mm hole with a small brass plate, by first waxing the sealing surfaces and then pressing together after reheating.Mounted on my turbo-pump vacuum system.THIS 200 YEAR OLD NATURAL PRODUCT WENT DOWN TO 10^-7 mbar!-No increase in pump-down time, ultimate vacuum or turbo pump load. I was stunned!So yeah, this is well worth having a stick of around! Only downside is, it can't be heated. duh.

author: Gregg
author_rank: Super Contributor
timestamp: May 23, 2021, 10:59:16 pm
content: It looks a lot like old fashioned sealing wax that was commonly used to seal documents over a century ago. It came in sticks that could be melted with a candle flame and dripped onto the closing flap of a document and a metal embossed unique seal form pressed onto the surface. It was somewhat pliable but friable enough to clearly show any tampering.

author: ChristofferB
author_rank: Frequent Contributor
timestamp: May 23, 2021, 11:11:02 pm
content: It does, and it smells like it too, with the notable difference that it cannot be used as sealing wax! I tried, ended up with all of the wax stuck in the seal

author: jpanhalt
author_rank: Super Contributor
timestamp: May 23, 2021, 11:13:22 pm
content: Quote from: ChristofferB on May 23, 2021, 10:23:56 pmBrings back memories. In 1959, I made a linear accelerator with a Van de Graaff generator that was based on a Scientific American Amateur Scientist article. Used the same recipe for my sealing wax, except I didn't add any coloring. A very nice chemist/glassblower at CalTech gave me the diffusion pump.

author: YetAnotherTechie
author_rank: Regular Contributor
timestamp: May 23, 2021, 11:23:54 pm
content: Quote from: ChristofferB on May 23, 2021, 10:23:56 pmBut how does it compare against plain-old epoxies??

author: LaserSteve
author_rank: Super Contributor
timestamp: May 25, 2021, 04:30:15 pm
content: Thanks...Giving it a try... ordered the materials.BTW = Venetian red is a form of Iron Oxide.Steve

author: Cyberdragon
author_rank: Super Contributor
timestamp: May 25, 2021, 06:59:06 pm
content: They still sell this vacuum sealing wax in meltable sticks. The common color is black now but it appears to be the same stuff (says heat resistant but also says melt at 130°C).However, the raw ingrediants are way cheaper, the going price for just wax (not including epoxy in a kit) appears to be 10 USD for per <1g stick!https://pr.vwr.com/store/product/4556338/apiezon-vacuum-sealing-wax-w

author: ChristofferB
author_rank: Frequent Contributor
timestamp: May 26, 2021, 08:43:25 pm
content: I think the electron microscope people use the Apiezon W to mount samples onto the translation stage reversibly.I just did a more practical test by mounting a standard ish quality BNC connector (Suhner) to a KF25 flange. Seen here with a faraday cup soldered on. I made an effort to also wax the dielectric/sleeve/pin interface, and to reflow the joint after tightening the nut.

author: Vtile
author_rank: Super Contributor
timestamp: May 27, 2021, 08:25:07 am
content: These similar (not same obviously) rosin based waxes are (or were) also used on gemstone grinding (..or cutting if we speak precious gems) fixtures. The trick at least with those is to heat up both the wax and the work pieces so as hot wax do not stick on cold surfaces as good as on hot/warm surface. Those are hard waxes (pure rosin and only minor additives) though like old document seal wax, while this one do have soft beeswax addition to rosin.One might want to do test on -15 to -20 deg. C temperatures if the pieces do separate (a trick to get the gemstone out of the fixture is to freeze the wax and stone to get less wax residue left on workpiece).

author: RoGeorge
author_rank: Super Contributor
timestamp: May 30, 2021, 11:00:47 am
content: Nice trick!Was hoping to see at least a glowing electrode at the end of the video, so frustrating!So far I could only find 3 years from the "Journal of Scientific Instruments" (on theInternet Archive: Vol. IV 1926-27 and Vol. V - 1928). I would like to browse more of those journals. Not looking for a particular number or a particular subject, just interested in vintage scientific instruments and history of science, in general.- Is there any place where I can get more years from the collection of "Journal of Scientific Instruments"?-ChristofferB, do you have any link for Vol. 13/1936 shown in the video (or can you PM a copy of it if the link is not public), please?

author: ChristofferB
author_rank: Frequent Contributor
timestamp: May 30, 2021, 11:14:52 am
content: Quote from: RoGeorge on May 30, 2021, 11:00:47 amThanks!No glow discharge this timethe thought didn't hit me. It might be a good way of cleaning something like a Faraday cup, actually.Journal of Scientific instruments is not as interesting as its spiritual successor "Review of scientific instruments - that's still running today"I can't share the paper, unfortunately, as I only have access through my Uni, and I don't want to rock the boat that much - journal publishers are notoriously unfriendly towards sharing..I can say, though, that aside from the faraday wax and the mention of Apiezon W, the rest was less interesting.Here is the review that linked me to that article, though:https://www.svc.org/Publications/History%20Corner.pdf

author: HighVoltage
author_rank: Super Contributor
timestamp: May 30, 2021, 11:35:29 am
content: Very interesting thread and videos.Thanks for sharing your vacuum knowledge

author: debreuil
author_rank: Newbie
timestamp: May 30, 2021, 10:40:32 pm
content: Great video and technique, i think I have all ingredients on hand, will give it a try -- thanks! For those interested, here is a link to Faradays Chemical Manipulation paper from 1827. So interesting reading these old publications!https://archive.org/details/b29309864/page/n7/mode/2up

author: LaserSteve
author_rank: Super Contributor
timestamp: May 31, 2021, 12:27:13 am
content: I made two small test batches. One with red oxide, one with ultra-fine alumina powder. I'M very happy with the product.Adding a tiny amount of Orange Oil to the melt made a flexible sealing material that while not useful for vacuum, is an otherwise interesting sticky compound. I'm waiting to see if the natural solvents diffuse out.Steve

author: amyk
author_rank: Super Contributor
timestamp: May 31, 2021, 01:58:52 am
content: Quote from: ChristofferB on May 30, 2021, 11:14:52 amThere's a little something called SciHub, courtesy of the friendly Russians...

author: ChristofferB
author_rank: Frequent Contributor
timestamp: May 31, 2021, 06:56:05 pm
content: Quote from: LaserSteve on May 31, 2021, 12:27:13 amOrange oil is mainly limonene; a terpene. hard rosin is resin that has its terpene content boiled off (turpentine) - you've basically just made a softer grade of natural rosin!Very interested in the alumina version! Maybe I should try that. Plenty of "ceramic" epoxies has alumina loading.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: June 11, 2021, 03:48:08 am
content: Older versions of the CRC Handbook of Chemistry and Physics have a section called "Laboratory Arts and Recipes" with many things like this. For vacuum wax it recommends equal parts by weight of beeswax and rosin. No coloring agent.Many of these old recipes laugh at modern safety standards. One for cleaning mercury, for example, calls for spraying the mercury in fine droplets into nitric acid, then heating to 110 C to dry. Many of the ingredients are difficult to buy for safety reasons (several call for asbestos). But they worked then, will work now, and didn't kill anyone quickly. Probably no one at all if care is taken.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 11, 2021, 03:59:19 am
content: And we have a lot of substitutes for those today, like ceramic wool instead of asbestos.Tim