Subduction Springback

11.5 x 15.3 x 2.5 cm

Springback book of cream laid paper, with leather-jointed paste paper endsheets. Spine covered in green goatskin over- and under-laid with golden bookcalf. Blind tooling.

This book, like the pale book, the traditional half-binding and the golden springback, is the remnant of an abandoned experiment in endpaper structures. The book blocks came in handy when I decided to explore the tradition of springback bindings.

(For more information on springback books, go to the golden springback binding notes. I won't duplicate the history here. I want to talk about the "subduction" process.)

Joining Leathers

Back cover: calf over goat

Front cover: goat over calf

The real innovation on this book was in the covering, though it was not entirely a success. It comes from my dissatisfaction at the ways I know of joining two pieces of leather.

When joining two straight-edged pieces on a book cover, one can either abut them or do a a certain amount of paring and over and underlay them. In theory, one can do the same with curved or irregularly shaped pieces, but that requires a much finer touch than I have. I tend to abut, which leaves the risk of gaps.

But the things I want to join are particularly troublesome. You see, I love the shapes that the edges of hides get into, as the three-dimensionality of goat or calf turns into the two-dimensionality of leather. The marks of the clips and hooks that help handle the skins as they are stretched and dyed add even more interest. But these edge pieces are so intricate, and often so stiff and coarse, that ordinary processes are almost too much trouble.

My solution is derived from back-pared onlays, which are another miraculous solution to an incredibly fiddly problem. Instead of a full onlay, why not do back-pared subduction? (my earthquake-aware Californian background is showing). Here's what I did:

1. I trimmed the leather to size. The underlay leather roughly followed the shape of the overlay, to reduce trimming and eliminate any hint of straight lines (which catch the eye).
2. Next, I pared the edge of the onlay. I wanted it thin, because otherwise the combined leather would be too thick to pare properly without cutting through the underlay entirely. But I didn't feather it, because I wanted the edge to look substantial.
3. Then I pared the edge of the underlay. I tended to feather-edge it, but that may have been excessive, because of the paring I did later on.
4. I pasted the onlay to the underlay and left it to dry in a press overnight.
5. The next step was the one I was least sure of. I could easily picture the pasted joint separating when the leather was going onto the book, or when it was contracting during the drying process. I wanted to stabilise the assemblage, so I glued a sheet of rice paper to it with water-soluble PVA (after testing that the PVA wouldn't take the surface off either leather).
6. Once the stabilising layer was dry, I started back-paring. I used two techniques in alternation:
   • sanding with a sanding block, which shows the high spots
   • paring with my French-style paring knife, kept sharp with frequent runs along the whetstone
7. I then pared the edges and hinges of the combined sheet as necessary and covered the book with the new combined hide.
8. I intended to remove the stabilising layer after the leather was dry, but it started peeling during the covering process. I did do the final tidy-up afterwards.

What Went Wrong

Color Bleeding

Although I tested the adhesive and leathers for surface damage, I didn't check colorfastness. It appears, based on the staining, that the PVA wicked some green dye from the goatskin onto the bookcalf. This may further limit the leathers that are suitable for this technique.

Sticky Fingers

Another problem was the way in which the stabilising paper came off during the covering process. Since the PVA was water-soluble (well, technically, water-reversible), the rice paper covering the joins began to come off in sticky, soggy clumps when the leather was wet with paste. And once it did start to come off, I had to remove as much of it as I could, or the remaining paper would have left dents after drying under light pressure. And leather covering is a fiddly process at the best of times - having to do it with PVA-sticky fingers, or take the time to wash my hands repeatedly, made it even worse.

Layer separation

The paste holding onlay and underlay together did fail at one point on the covers, and without the stabilising layer, the structure would have come apart. So the paper was of use.

Lessons Learned

Springback books are cool.

I will have to do more of them. I would particularly like to try the technique where the spring is built up of layers all the same size (leading to sloped grooves) rather than of layers measured one by one (leading to straight edged grooves, but taking ages).

Try more back-pared subduction joins

I have three ideas:

1. Use a different adhesive.
   I need to find one that won't wick dye from one leather to another or dissolve when the paste is wet, but will come off cleanly. I will have to test my other PVAs and paste options.
2. Only stabilise part of the subduction
   If I glued stabilisation layers only at the turn-ins at top and bottom, and relied on the paste for the remainder of the adhesion, I could reduce any visible effects of the gluing. This is highly dependent on a good internal adhesion to make the join last through the pasting process.
3. Pare together, mount separately
   If the paste join won't last through the mounting process, an alternative would be to paste the joints together for paring, them gently peel them apart. Then I could paste the substrate layer onto the book, wait until it was dry, then add the onlay part in a separate step. This relies on being able to re-align the pieces precisely enough to match the paring thicknesses.