Vintage Kester "44" Resin (not Rosin) Solder

[Dave8266]

I picked up a hefty roll of vintage Kester solder this afternoon, and was wondering if anyone knows how old this might be?

The "44" labeling is prominent, but curiously it is indicated as being a "resin" flux, not a "rosin" flux as Kester now calls it.   The earliest dated reference I can find is from 1996 (archive.org for Kester's website), and it was "rosin" then as well, so this is at least 26 years old.

The formulation is also interesting.  "3S/61(1/2)T/35(1/2)L"... which I would interpret as being Sn61.5 Pb35.5 Ag3 in modern alloy nomenclature.    It's not in Wikipedia's list... the closest being either Sn61Pb36Ag3 ("POS61") or Sn62Pb36Ag2 ("Sn62").   I did find it in Kester's "Alloy Temperature Chart", in the "For Reference Only" section as the exact Sn61.5Pb35.5Ag3, so I would assume this to be a legacy alloy that is no longer in use...  (and also, that this indicates it isn't just Sn62Pb36Ag2 with the numbers rounded for convenience).
https://www.kester.com/knowledge-base/alloy-temperature-chart

(and for reference, the melting range is "205C" or "401F" - neither of which is a range, so I presume this to be a eutectic alloy.)

[bdunham7]

Since they call it '44' I'd assume that resin is just the name they used instead of 'rosin'--they're both pine based.  Or, perhaps it is their old formulation.  It looks like that is a eutectic (or very close) hard silver solder with a somewhat higher melting point than the newer formulas.  It's probably valuable for certain niche applications, like solder terminals on old Tek scopes.  I'm not sure how good the flux will be after all this time.  Maybe you can sell it by the meter on eBay!

[TimFox]

Looking at the analysis posted at that Kester site of a normal leaded alloy with 44 flux showed only lead (obviously) and chlorine above the MDL (minimum detectable level) at the test lab.

[jpanhalt]

I had to look up the history.  Here is a good summary: http://progress-is-fine.blogspot.com/2013/05/we-used-to-make-things-in-this-country.html

Company was bought by Litton in 1967 and resold to Northrop in 2006.  The absence of a ZIP code suggests it is quite early (1950's); however prior to ZIP codes, addresses still used a city zone for large cities, e.g., Los Angeles 22, Calif.  So, that may not mean anything.

It's hard to tell.  I have a role of Kester "44" undated that carries the Litton name.  It is labeled ""44" Resin Solder;" although, the side of the box says rosin.  "Resin" must be part of the trademark and seems to have little bearing on the age

The absence of Litton in the address, makes me think it is either pre-1967 or post-2006. 

Edit: If it lacks a barcode on the bottom, that might be consistent with the earlier date.

[Dave8266]

Thanks everyone, that's great information.   

The bottom of this particular spool is actually identical to the top, just without the information stamped in the blanks.  No barcode or any other differences.

Based on jpanhalt's link, it looks like the age of this roll would then be bounded roughly between 1931 (opening of the Brantford plant) and 1967 (Kester's acquisition by Litton Industries), given that this roll does not have the LI logo or branding.  Furthermore, the last patent listed on the spool, 2052740, was issued Sept 1, 1936.   (https://www.freepatentsonline.com/2052740.pdf)  So that narrows it down from late 1936 through 1967-ish.  ("ish", given that they likely took some time to rebrand and work through already printed spools after the acquisition.)

I also noticed that later (Litton-era) Kester spools appear to have a third location listed - Anaheim, California.  Does anyone know when that location opened?