Splicing Tape

Today when I say "splicing tape" people assume magnetic tape or film. But the term goes back much further. In my career I've mostly used 3M scotch splicing tape when editing 1/4" recording tape. But a bunch of other companies sold it: GE, Sony, Ampex, Silvertone, Hitachi, BASF, Audio Devices and of course Radio Shack. I saw a roll once from the Burroughs Corp. It's sometimes unclear if it's intended to splice film tape or magnetic tape from the packaging alone but in a pinch, either would probably work. I think TME and Splicit, are the popular makes today.

The patent for the modern splicing block was filed in 1950. It's patent # US2599667, granted in 1952 to audio engineer Joel Tall. [LINK] He called it an "Edi-Tall" and it was an aluminum block with both of the standard 90 degree and 45 degree slots you'd immediately recognize. But his tape groove was slightly concave, some makes are flat. The Edi-Tall was sold through Xedit and also sold Editabs, precut segments of splicing tape.  

Obviously magnetic tape already existed as did the splicing tape. The block solved a problem that already existed. In the prior art he cited miter boxes and a film splicer US2552148 (below) which he basically copied. In 1949 R. H. Carson invented a "Tape Splicer" whose design is very similar to Tall's but was meant for film!  Around 1952 the "Jifffy Splice" hit the market which also looks derived from the Carson patent.

How far back does splicing tape go? Not as far back as magnetic tape. Fritz Pfleumer invented magnetic tape in 1928. Fritz was using paper tape which is not very durable. But it was still used into the 1940s along side early plastic tapes, but there was no dominant standard. In 1947 Minnesota Mining and Manufacturing introduced a polyester based tape. That's polyethylene terephthalate for the plastic fans out there. That material rapidly became the standard. 

Minnesota Mining didn't have a completely clear ownership of the innovation, hence a lawsuit with Technical Tape Corp in 1954. That suit spells out how narrow their claim is, competing patentees, other manufactures of similar plastic tapes: Van Cleef Bros, to whom they even had to pay a royalty. it also names some of the few competing products, what it calls "homart" plastic tapes which are basically electrical tape. It contains some genuinely funny testimony:

WWII delayed the introduction of magnetic technology to the west. Some enterprising folks shipped home equipment from Germany like Jack Mullin, who took a Magnetophon K4 to AMPEX who then created the Model 200 in 1948. That narrows down our time window quite a bit. Only after 1948 could  a market develop for a polyester-backed adhesive tape that will stick to polyester-backed magnetic tape. That cellophane tape is probably what you would have used before the polyster was available. 

Early documentation is poor. Splicing tape is a only supporting character in the story of magnetic recording. I found a 1959 military manual that describes the splicing kit used by Air Controlman. The 1952 book, Making Radio Work for You aimed at U.S. Dept. of Agriculture extension agents doesn't specify polyester, just the distinction between plastic and paper.

I found an advertisement in Electrical Industries magazine from 1945 about the Magnetophon. It describes the demonstration, where they break the tape and splice it with what sounds like an adhesive, or solvent. There is no splicing tape used because it didn't exist yet!  The timing also means that it must be  a non-polyester plastic. Had it been paper I think they would have described it as a glue. At that time, PVC existed but if the tape was celluloid (cellulose acetate), that material can be melted and fused with common acetone; which sounds more like the demo scenario described. 

"The American broadcasters were amazed by a recording of a musical program being transmitted. It was played back immediately and the quality was better than good. There was no surface noise. The tape was purposely broken and spliced immediately with a dab of chemical. Recordings can be edited to the syllable by splicing. Tape seldom breaks, however."

1945 is as far back as the trail goes. If you look at the term "splicing tape" in any document from before about 1945 it will refer to electrical tape. This is a non-vulcanized "rubber" tape. You will see brands like Okonite, Okoprene, and Kerite to name a few.