Here’s my notes about rounding and backing using Gelatine. Below is a description – I hope some of its useful – there are bits that are arrived at through the “suck and see” method.
We use an electrically heated waterless glue pot in which we put a small amount of water (maybe one or two cup fulls or so) then cut up, into thin strips, leaf Gelatine only a few leaves – maybe 3/4? It’s all done really by consistency – if you stir in the gelatine until completely dissolved the adhesive should be slightly thicker than water but not so thick it can’t be brushed on – slightly gloopy. If its too thin add more gelatine – one sheet at a time stirring it in as you go. If too thick add more water. I guess if you have an old saucepan you could just cook up in that – but you would need to work fast to avoid the gelatine becoming too thick or setting because of cooling.
With the book knocked up to the spine edge and head between two waste pieces of board that are cut to the same size as the text block – put a heavy weight on. For relatively standard thickness of board we aim for around 20% swelling – if the fore-edge is 20 mm the spine should be around 24mm.
In order to prevent the glue running in between the gatherings you may want to rub down the backs of the sections at this stage with a folder to close the gaps up a bit.
Glue up the spine – brushing off the ends and ensuring there are no gaps left between the sections. You may wish to avoid glueing over the tapes at this stage to allow the sewing threads to move during the Rounding and backing process.
Leave the book for maybe 10 – 15 mins until the adhesive is touch dry – try not to leave it too long as the book will set too hard and if its too short you may damage the backs of the sections.
Mark the joint height on the waste sheet with a very sharp pencil to the exact thickness of the boards. Round the book as usual then very lightly tip on parallel backing boards to the pencil lines on the waste sheets. Back the book trying to fan the sections out rather than distorting them. Once you are happy you can either re-glue the spine with gelatine or if there is a reasonable amount on there just soften it with warm very slightly damp cotton wool. Leave the book to set but with the press backed off slightly (hand tight) for maybe an hour or so at least – If you need the press and backing boards put the book between pressing boards (into the joint) and put a weight on.
As far as spine linings – we put an initial thin cotton lining on with gelatine (normally after attaching the boards and endbanding). The cotton is a natural unbleached Voile or Scollata. It’s best to use as little adhesive as you can get away with on the book and work gelatine in with your fingers through the cotton to aid adhesion and add strength. Let this dry. Subsequent paper linings can go on with reversible PVA or EVA. The first paper lining is generally cut to fit between the tapes to help level everything off.
Apologies if a lot of this is obvious – I like to work the whole process through in my mind when typing to avoid missing stuff!
Hope this helps, Good Luck, Stu.
Sweet Thames Run Softly 