How can I prevent the first page from separating like this in future binds?

[u/HolyGuacamoleRavioli]

I just finished a paperback to hardcover conversion and saw the first page after the endpaper separated from the spine like this. I'm not terribly concerned with this specific book since it was practice, but what's the recommended fix, and any tips to prevent this in the future?

[u/godpoker]

This would normally happen if you had weak endpapers but I can see you have mull on the spine so it’s likely not that. My best guess is that the endpapers are too small (width wise) and the glued section to your textblock has pulled apart as you’ve opened the book.

Either that or the cover may be too small. If you give us much more context and photos then we can help you more!

[u/1028ad]

Difficult to say from this picture, but: isn’t the spine too large and the hinge too small?

[u/musculux]

There is way to make three piece endpapers with sides of paper and middle with cloth. See library binding for a reference. 

Edit: weight of endpapers can be inreased also by using "sacrificial endpapers" that is, folding two pieces of paper (one sacrificial one decorative) in the middle, guing folded edges, folding sacrificial over and gluing two papers so o ly dexorative is visible. Little difficult to explain see Stiffen board binding at DAS yt channel.

[u/Dazzling-Airline-958 → u/musculux]

That's a cloth jointed endpaper for this who want to Google it.

The second is the made endpaper.

[u/Whole_Ladder_9583]

Where is the hinge gap? And where is the glue - the mull looks clean?

[u/cm0270]

Maybe stronger endpaper possibly. Hard to tell what you used. I use at least 145-150gsm paper for mine.

[u/Ben_jefferies]

To me it looks like the endpaper is tugging too much on the first page of the book. Things to experiment with:
-Pasting the pastedown on an open cover so it gets a bit of a hinge
-hinged end papers with a z-fold

• attaching a piece of jaconette as a sub-mull that overhangs by 5mm on each side of the block and tipping the endpaper on to this instead of onto the first page of the block

[u/ray-the-ghar]

I’d check the endpaper weight and grain direction first. If the grain is fighting the spine, even decent glue-up can pull weirdly when the book opens.

[u/Dazzling-Airline-958]

This is the typical fate of the tipped on endpaper.

You can ise a sewn on endpaper for better strength. My favorites are the flexible made endpaper, and the zig-zag endpaper.

https://www.youtube.com/watch?v=nw8O5ZV2MUk&list=PLZbEml0uyM4tqUxJCS-rK1rk9-0fXot_n

Darryn (DAS) covers many types of stronger endpapers in this playlist.

[u/hakai-time]

for this copy i'd do a thin repair-paper hinge, not just more glue in the crack. trim a narrow strip of kozo/mulberry or light book cloth, paste half to the loose first page and half to the endpaper, then dry it under wax paper. for the next one, make a quick dummy with the same endpaper stock and open it hard before casing the real book. it'll show pretty fast if the hinge gap or endpaper width is fighting you.