How soft putty grips a painted wall
Sticky tack works by making close contact, not by hardening into a permanent bond. Pressing it against a poster and wall squashes the soft putty into tiny surface grooves and bumps. The greater the contact, the more places the tack can cling through weak attractions between materials.
Because the putty never fully cures, it remains pliable instead of turning into a rigid adhesive. That softness lets it keep adapting to the surfaces as they shift slightly, helping the poster stay put without requiring a glue-like layer that sets solid.
Why it can come off again
The hold is firm enough to resist the poster’s gentle pull, but the tack can deform when you peel or roll it away. Rather than breaking a hardened bond, removal changes the putty’s shape and gradually separates its contact from the wall. Using several small pieces also spreads the poster’s weight across multiple spots.
Paint condition and surface texture still matter: dusty, rough, or fragile paint can make the grip less reliable or removal less clean. On a smooth, sound surface, the useful tradeoff is that the tack conforms while pressed, then can be lifted away instead of remaining as a cured adhesive.
