Tape Splicing Thoughts

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Tape Splicing and Related

Introduction

I’m not too sure where to start with this one, because the more I think about it, the more I realise what I don’t know, and how I have been winging it for years, but here goes.
I would estimate that most of us have encountered and/or made tape splices of one sort of another, but how many of us have actually thought much about it? Perhaps it’s just me who hasn’t?

Hopefully pretty much everyone would at least know which side to apply the joining tape (i.e. not the side that is in contact with the head(s)), but what about the characteristics of the joining tape itself, what splice angle should the joining tape be cut at, what splice angle should the ends of the magnetic tape be, and what other factors should be taken into account?

Splice Angle

Perhaps there are other angles for audio cassette tape, 8mm and ½inch video tape etc, but I here I have a typical splicing block for ¼ inch audio tape – see photo below. It can be seen that there are three splicing angles available – 90 deg, 60 deg and 40 deg (with respect to the tape running edge). I don’t know whether other angles are offered by other block manufacturers.

Here are some (possibly) obvious thoughts:-

Magnetic Splicing Impact on Impact on Tape Head(s)
Splice Tape Pinch Roller
Angle Angle

90 deg 90 deg Quite a bump All tracks are affected simultaneously
60 deg 60 deg Easier passage The splice sweeps across the tracks fairly quickly
40 deg 40 deg Easiest passage The splice sweeps across the tracks slower
90 deg 60 deg Easier passage All tracks are affected simultaneously
90 deg 40 deg Easiest passage All tracks are affected simultaneously
60 deg 90 deg Quite a bump The splice sweeps across the tracks fairly quickly
60 deg 40 deg Easiest passage The splice sweeps across the tracks fairly quickly
40 deg 90 deg Quite a bump The splice sweeps across the tracks slower
40 deg 60 deg Easier passage The splice sweeps across the tracks slower

Other combinations are no doubt available, but in all cases I have assumed that the join at the magnetic tape ends is made to precisely butt up together with no gap and no overlap.

By the way, if you are now concluding that a 90 deg splicing tape angle is less desirable in all cases because of the bump through the pinch roller/capstan, then it might be time to re-think that. I’m not saying that it is ok for every scenario, but it might actually be an advantage in some cases, for instance, I understand that some machines (eg some NAB Broadcast cartridge machines) are designed to locate a splice and place it just after the pinch roller/capstan. This is good practice as it puts the splice out of reach for any recording. It finds it by, unbelievably, detecting the bump when it slightly displaces the pinch roller. I conclude that if the splice transition was far too gradual and smooth, the splice detection might actually miss it. I digress.

Please read on ...

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Sorry, that bit above was supposed to be a nice neat table, ow well, best plans and all.

Let's carry on ...

I also observe that all my unmolested audio cassettes, 8-track cartridges, NAB cartridges, 8mm/Hi8, VHS and Betamax/Betacam video tapes have 90 deg splices (both magnetic tape and splicing tape/foil) are used at the interface between the leader and the magnetic tape. Perhaps this is universal? So perhaps the variables only get considered when making a splice that joins magnetic tape to magnetic tape?

Anyhow, the splicing block lends itself to preparing a decent matching magnetic tape butt at the splicing angle chosen, but only long as both halves of tape are located where required and held in their exact positions when the cutting blade is used (easier said than done!).

The splicing joining tape that’s normally available for use with such blocks is another kettle of fish. It behaves like a mad box of frogs and even if you manage to perfectly align it in the block. It has an affinity with the block and will, given any change whatsoever, stick itself to the block sides or the bottom surface at angle it pleases. Even if you did manage to perfectly align it cut one end to the desired angle, you’ve then got to wrestle with it again to drag it along the splicing block to cut the other end. It should also be noted that the splicing tape I have (and is typical I think) is slightly less wide than the ¼ inch tape so you have to wrestle it to the centre as best you can. It makes you think that there’s got to be a better way.

If you think you’ll get away with putting it into the slicing block sticky side up, then think again, the cut angle will, naturally, be reversed!

Of course if you are inclined to persist with attempts to prepare the splicing tape in the block like this, it’s arguably best to form the angle cuts in the splicing tape first, else you’d have to take the perfectly prepared and aligned magnetic tape out of the block to vacate the block for splicing tape use and then you’d have to remove that, put the magnetic tape back in and then try to realign it.

Splicing Tape Characteristics

The following provides food for thought:-

• A long-lived and robust splice is needed, so the adhesive should not dry out;
• The tape adhesive should be effective without the possibility of sticky residue oozing out causing sticking turns of tape and/or fouling up head(s), pinch roller or capstan;
• The splicing tape should not overhang the sides of the magnetic tape;
• Whilst forming a robust join, the splicing tape should not be excessively thick as this might impede its passage through the machine, especially the pin roller/capstan.

Do we need to consider any other aspects, eg:-

• Colour – why are there so many different colours, does it matter;
• Opaque or transparent and is it relevant;
• Is the surface finish of the backside of the splicing tape relevant;
• How long should the splicing tape be;
• What to do about any foil stopper/track changer (which is actually fixed on the head side of the tape) and also whether or not the splice at this point needs any reinforcement with standard splicing tape to the rear etc.

More to follow ...

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As a small child and teenager, I used to join tape with ordinary transparent parcel tape (like Sellotape™). Yes I know! I can see you all cringing now! At the time, it seemed to be ok in the majority of cases, but of course now, I’m cursing what I did, as said splices, now well over 45 years old, simply part company whilst leaving dried on residue. Of course there is also a danger that a tape with a parting splice might end up getting mangled in the pinch roller/capstan (not good). I came across one of my earlier audio cassette recordings recently (1975 I think) and decide to play it. There was a mistake right there! I forgot it was a spliced one and yes, the join parted company. I wasn’t fast enough to stop the machine in time and only got there in time to see the tail of tape disappearing into the sealed cassette shell and on to take-up spool! I then spent ages trying to crack the thing open without damaging anything!

I may be in for more fun yet of course as when Scotch Magic Tape™ came out, I thought I’d try my luck with that. Interestingly the matt backing surface finish provides a good deal of grip and it seems to slip through the pinch roller/capstan with ease – even a 90 deg one. Also, should I wish, I can easily achieve a decent angled splice without fighting the box of frogs. Let me explain …

Prepare the magnetic tape ends in the block at the required angle as normal. Leave the tape undisturbed in the block, bring the magic tape across the magnetic tape surface at the angle required (using the block slots as a guide) and carefully press down, avoiding any magnetic tape movement. Remove the assembled splice (and overhanging Magic Tape™ from the block. Take care not to let the Magic Tape™ stick to anything that it shouldn’t, then trim along the sides with some decent non-magnetic scissors. OK, this last bit is a little tricky, but with practice it is possible to achieve a great result by neither shaving off any magnetic tape nor leaving any Magic Tape™ overhanging. It may even be possible to trim it in a household guillotine, but I haven’t actually tried that yet.

With practice, it’s even possible to create a reasonably decent splice without the block (just a keen eye for alignment and steady hands).

I did wonder about the thickness of Magic Tape™ versus that of ‘standard’ splicing tape (whatever that means). Within the capabilities of my measuring equipment, I have concluded the following:-

• Magic Tape™ 0.06mm
• Standard Splicing Tape (for audio cassette use) 0.05mm

So, not really that different, if at all.

What I will say, and this may seem rather surprising, is that my earliest Magic Tape™ efforts are still holding up very well. Nothing nasty going on and the splice is as robust as it ever was. I’m not necessarily advocating Magic Tape™ for this duty by the way, it’s just an observation.

Actually, what is the expected life of ‘standard splicing tape’ anyway?

By the way, when I say, ‘prepare the magnetic tape ends in the splicing block’, it might well be the case that you don’t want to cut any tape at all away for fear of losing some recorded material. It may be perfectly legitimate to re-make the ends as you found them (assuming that they still mate reasonably well. I mean you don’t want any of the sticky side of the splicing tape not covered by magnetic tape else you’ll be in for it).

More ..

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Final Thoughts

Is the type of splice dictated to by the:-

• type of magnetic tape;
• magnetic tape thickness;
• type of machine in which the tape is used;
• type of recorded material – audio, data, video etc;
• whether or not we are dealing with existing recorded material or making preparations for a new recording;
• tape speed?
or all of the above?

What might be those rules and how does that translate to a practical approach when attempting to create a successful and applicable splice?

What I do know is that I am owe of people in the TV industry who had to make real physical splices in 2 inch? Tape by physically looking at video fields revealed by the use of a special ‘developer fluid’ and without seeing an actual image on a monitor. Of course you only get one chance!

I wonder what the splice angle was for loops for the likes of the Wem Copicat™?

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More photos ..

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Just to clarify the table, the items contained therein, were in the following order:-

Magnetic Tape Splice Angle, Splicing Tape Angle, Impact on Pinch Roller, Impact on Head(s)

Sorry that it didn't come out all neatly tabulated.

[Restoration73]

It depends on the application. Splices go through quickly at 7.5 and 15 ips and I prefer
a 90 - 90 join. If the same type 1/4" tape is used the join is inaudible.
Editing open reel was simplified by using the BASF splicing tabs, a dispenser with
pre-cut tape about 2cm long with 45-45 ends, I am only aware of two colours, white for
LP and blue for SP. Together with the EMI block, splicing tape or adding leaders was
simplified. I only join cassette tapes in an emergency.

[barrymagrec]

When I worked in a broadcasting organisation all the splices were 45 degrees (EMI block)

Mind you, that was full track mono at 15 ips.

[paulsherwin]

Splicing cassette tape is very difficult because of the narrow tape width and low playback speed. With normal tape at pro speeds the angle of the splice doesn't really matter. Sloping splices are supposed to give a crossfade effect at the edit point.

Scotch Magic Tape does make quite good splicing tape in an emergency, but is obviously the wrong width and must be carefully trimmed with a blade or sharp scissors afterwards. The proper stuff is better, though it too fails after a few decades.

[Kentode]

The only thing I can add is that it's designed for right-handed people! Just what us left-handers want, a razor sharp blade in the wrong hand!

[Nickthedentist]

Originally Posted by paulsherwin

Splicing cassette tape is very difficult because of the narrow tape width and low playback speed.

I used to do it a lot as an impecunious schoolboy, though I doubt I could do it so well now.

The main problem I remember was that the tape was reluctant to lie flat, and was often attracted to the splicing tape by static effects.

[Michael Maurice]

Never never splice video tape. A splice however good it is will smash the video heads.

[Nickthedentist]

...unless it's to the clear leader (e.g. if you're discarding a chewed or worn chunk at the beginning of a cassette) and so the v/heads will never "see" it.

[vidjoman]

Originally Posted by Kentode

The only thing I can add is that it's designed for right-handed people! Just what us left-handers want, a razor sharp blade in the wrong hand!

If you turn it upside down the slope Will be the opposite direction.

[llama]

When I did a lot of splicing of quarter-inch tape I would normally use half-inch splicing tape laid across the tape join at about 45 degrees and then trim.
Graham

[Cathovisor]

The oft-forgotten reason for the 45 degree splice used in the broadcast industry is that it gave a rapid crossfade of programme material thus avoiding that jarring 'bump' mentioned elsewhere.

[Kentode]

Originally Posted by vidjoman

If you turn it upside down the slope Will be the opposite direction.

No it won't! Try it...

[vidjoman]

I would normally make a splice in a moment of silence. Using a fast tape speed gives you the most space to make the splice. I did, when I was young, using simple slow speed tape decks do some splicing to edit recordings of pop groups, but the results were not very good.
So graduation to 15ips meant almost perfect splices every time. I used the EMIblock, similar to the one shown above. Only extra tools needed was the razor blade and a chinagraph pencil to mark the tape. Always use the correct splicing tape or you will get premature failures.

[vidjoman]

Originally Posted by Kentode

No it won't! Try it...

Sorry Ken. What I really meant is that with the block shown, it will move the diagonal slot to nearer the opposite end and make it easier to use.

[Kentode]

No problems, l did actually turn mine upside down the first time and was most disappointed.