The method described here does away with the traditional sticky tape so often used in roll repair. Although the repair is visible as it makes the paper transparent, it goes long way to resolving most of the problems associated with sticky tape.
Some of those problems include the inability of plastic sticky tape to change size with the paper in response to the day to day changes in humidity causing the paper to distort, and possibly worse is that over time the plastic tape tends to shrink, causing the paper to distort even more, maybe so much as to make the roll unplayable. Finally, even specialist archival repair tape adds thickness to the paper which can lead to tracking problems from the roll being wound unevenly, perhaps causing further damage.
This method exploits the fact that when paper tears it does so unevenly leaving an overlap of rough fibres. For this reason I would only recommend it on fairly fresh tears as on old ones the fibres along the edges of the tear can be worn away by the tracker bar or spool flange.
Here is an example (fig.1) of a typical tear on the edge of a roll.
A close examination revealed that the edges of the tear were still fresh enough for this mend. A word here about ironing would not go amiss. In some circumstances it is beneficial to iron the damaged section before mending. I have nothing against ironing, (unless it is a pile of laundry!), but do be careful about using steam. Steam causes the paper to shrink and is likely to distort the paper causing further roll playing problems. In this case, although the paper is creased, there is no need to iron.
Using a sheet from one of those Post-it notepads that have a re-usable sticky stripe on the back, press one edge of the tear down on to the sticky part (fig. 2). Check carefully that the "lower" part of the tear goes down first. I find that it is advisable to make the Post-it less tacky by rubbing it with my fingers first as some roll paper is quite fragile and little 'stickyness' is actually needed.
Press the other side of the tear down (fig.3) and rub it firmly with the back of a fingernail.
The paper should now be stuck flat down and the tear almost invisible. Take the brush from a bottle of cyanoacrylate "instant" glue, make sure it is almost dry by touching it against a piece of tissue and at the same time, check there are no drips running down the shaft. Run the brush lightly along the tear and the glue will wick into it, joining up the broken fibres (fig. 4). It is important to use as little glue as possible as too much may cause the Post-it note to become glued as well.
Immediately after applying the glue, burnish the mend (fig.5) by rubbing firmly with the back of your fingernail. This will flatten the still soft glue making the mend totally smooth.
Turning the roll upside down, carefully remove the Post-it note, pulling along the tear. Not across it (fig. 6).
You should now have a durable repair (fig. 7) that is as flexible as the surrounding paper and has added no thickness.
The proof of the pudding is in the eating it is said, and although the repair is visible (fig. 8), the roll now plays as if it had never been torn.
As in all things, one gets better with practise. Try your skills on some scrap paper first before attempting to mend your valuable roll and of course, take care of that glue, it sticks skin very effectively!