Blocking
Blocking is when two printed or coated surfaces stick to each other—for example, pages sticking together inside the book, or a cover sticking to another cover in a stack. When you pull them apart, you may see:
- torn paper fibers
- surface damage
- ink or coating transfer
- Areas that look “pulled” or “peeled”
Blocking is most common when inks, coatings, or laminates are not fully cured or when books are stored under heat and pressure.
Consumers often describe it as:
- “Pages are stuck together”
- “My book feels glued shut in spots”
- “The cover stuck to another book”
- “It tore when I opened it”
- “The ink pulled off when I separated the pages”
Also Known As: Sticking, adhesion, ink blocking, coating blocking, lamination blocking, tackiness, blocking in stack.
In simple terms: the surface wasn’t fully cured/hardened, so it stuck to the surface it touched.
What causes blocking?
Blocking is usually caused by a combination of tacky surfaces + pressure + time + heat.
1) Ink/coating not fully cured or dried
If ink, varnish, UV coating, or lamination adhesive isn't fully cured:
- Surfaces can remain slightly tacky
- Under pressure, they bond to the adjacent sheet
This is more likely with:
- Heavy ink coverage
- Thick coatings
- Rushed finishing schedules
2) Heat and humidity during storage or shipping
Warm conditions soften coatings and increase tack:
- Hot trucks/warehouses
- High humidity
- Books stored near heat sources
Heat \+ pressure can turn “almost cured” into “stuck.”
3) High pressure in stacks or tight packaging
Even a slightly tacky surface can block when:
- Books are tightly shrink-wrapped
- Heavy cartons stack on top
- Covers are pressed together in transport
4) Certain coatings and finishes (especially high-gloss or soft-touch)
Some finishes are more prone to blocking if not fully cured or if stored hot:
- High-gloss UV
- Some aqueous coatings
- Soft-touch or rubberized coatings (can feel tacky under heat)
- Some laminates depending on film/adhesive type
5) Incompatible or poorly performing coating/ink combinations
Some combinations don’t “play nice,” leading to:
- Slow cure
- Surface tack
- Higher risk of sticking in stack
6) Set-off powder or anti-block treatments missing/ineffective (offset)
In some workflows, powders or anti-block additives help keep sheets separated. If insufficient:
- Sheets can stick
- Transfer and tearing become more likely
How to identify blocking in a book
What it looks like
- Pages or cover surfaces that feel stuck
- A “pull” sensation when separating pages
- Paper fibers tearing (rough, fuzzy damage where they separated)
- Ink/coating transfer (one side loses ink/finish, the other side gains it)
- Glossy areas that become cloudy or scarred after separation
Blocking often leaves damage that looks like:
- The surface layer was peeled off
- A patch was ripped away
Where it shows up most
- Coated photo sections (glossy pages)
- Heavy solid ink areas
- Covers with gloss UV or soft-touch finishes
- Books shipped/stored in warm conditions
- Tightly shrink-wrapped bundles
Simple at-home checks
Check A: Gently fan the pages
If some pages “clump” or resist separating, blocking may be present.
Check B: Look for paired damage
Blocking typically creates matching evidence:
- A damaged spot on one page and a corresponding mark/transfer on the facing page
Check C: Smell/feel tackiness (carefully)
Some blocked surfaces feel slightly tacky or rubbery, especially if warm.
Common look-alikes (and how to separate them)
1) Binding glue seep (adhesive seepage)
Sometimes adhesive from binding can accidentally stick pages near the spine.
- Glue seep is usually near the gutter/spine edge and may look like hardened glue
- Blocking can occur anywhere printed/coated surfaces touch, often in image-heavy areas
2) Set-off / Offsetting
- Set-off is ink transfer without necessarily sticking strongly; pages separate normally but show a transferred image
- Blocking involves actual sticking and sometimes tearing/peeling
Blocking can include set-off, but with stronger adhesion and surface damage.
3) Smearing
Smearing is rubbed wet ink; pages don’t usually “bond” together. Blocking is adhesion.
4) Static cling
Some coated pages can cling briefly due to static, but:
- Static doesn’t tear fibers or peel surfaces
- Static usually resolves easily and doesn’t leave transfer damage
5) Humidity warp/cockle
Humidity can make pages feel “grabby,” but again:
- No tearing/peeling
- No paired transfer damage
Impact on book quality and readability
Readability
Blocking can prevent reading entirely if:
- Pages are stuck and tear when separated
- Text/image areas get damaged
Appearance
- Torn fibers and peeled surfaces look like damage
- Glossy photo pages can be ruined
- Covers can scar, cloud, or lose finish patches
Durability
Once blocking happens:
- The surface is physically compromised
- Affected pages are more prone to future scuffing/tearing
Industry standards and “acceptable tolerances”
Blocking is generally considered unacceptable because it prevents normal use and causes damage.
Usually acceptable
- Brief, light sticking that separates cleanly with no damage (rare in consumer books, but can happen with certain glossy stocks)
Usually not acceptable
- Pages that tear or peel when separated
- Repeated stuck sections
- Ink/coating pulled off
- Any damage that looks like ripping or delamination
A useful rule of thumb: If pages stick and separation causes visible damage, it’s beyond acceptable variation.
What you can do as a buyer
- Don’t force stuck pages aggressively—this can worsen tearing
- If pages are stuck or peeling
- Photograph the stuck area before separating further
- Photograph any transfer/tearing after separation
- Request a replacement (blocking is a legitimate defect/damage)
Helpful wording for support: "Pages/surfaces are blocking (sticking together). When separated, the coating/ink tears or transfers, damaging the pages."