Smyth sewn: thick/visible glue vs thin/invisible

I am wondering what the difference is between smyth-sewn books that have a visible glue layer vs ones that don't. In particular all of my modern reference books have a nice, thick glue layer on the signatures like this:




However the older reference books in my library don't have a thick glue layer. It is completely invisible, e.g.




To clarify: I have taken apart one of the "thick glue" ones and it does indeed still have horizontal stitching between the signatures. So the glue is not being used to hold the signatures together horizontally.

Also, I have noticed that all of the lower quality/imported smyth-sewn books in my library have a thin/invisible glue layer, whereas the ones from respectable publishing houses that have good quality covers etc all have a thick glue layer like in the top image.

Also, just intuitively it seems like a thick glue layer - all other things being equal - is more durable than a thin one in a smyth-sewn book. But I have received advice telling me otherwise which has left me a bit confused.


Thanks

 

Seriously nobody answered this question? I came here wondering the exact same thing... trying to get some insight on binding detail. Does someone know the answer?

 

Hello, I will try to answer your question.
Pay attention in your book what kind of paper is used, if offset paper is 60-100 g/m2 then it is sufficient to use Water-Based Adhesives (PVA) glue. Such paper absorbs glue well and it is necessary to apply a thin layer, it is not possible to see the thickness with your eyes. The book opens very well and is durable. Unfortunately, not all printing houses have such equipment that applies Water-Based Adhesives (PVA)glue and dries. Since there is water in the glue, it takes time to dry. If the book consists of glossy paper 90-170 g /m2, then it is necessary to use Water-Based Adhesives glue for good adhesion and elasticity of the spine, then apply PUR glue with a thickness of 1-1.5 mm, depends on the thickness of the book block. It's in idel)))) Most printing houses do not have the necessary equipment and use only hot melt glue for any paper to process the spine of the book block. Like in your photos. Advantages of using hot melt glue for production. Affordable inexpensive compact machines. This glue seizes quickly and can be immediately cut from three sides of the book block. The glue is stored in a hot bath for a long time. But there are disadvantages of hot melt glue. I think so, I don't want to offend anyone. If anything , I 'm sorry in advance . Hot melt glue is designed more for magazine products where there is no sewing. If hot melt glue glued a glossy paper book open 180 degrees between the notebooks, the glue may peel off from the paper or crack, In any case, if you often flip through the book, the glue will peel off.For a good bonding of hot melt glue, the conditions needed are temperature and loose paper. Since glue has been living in a hot tub all its life, it loses its properties and burns out the particles. Glossy paper does not absorb glue well.