The silicone stays tacky: it is not “drying”

Curing is not drying

Acrylic loses water and goes hard. Silicone reacts with air moisture, from the outside in. If humidity is missing, it is too cold, the cartridge is dead, or the bead is a 15 mm sausage with no backer, the core stays paste.

As a rule of thumb, in typical lab conditions (about 23 °C and 50 % relative humidity) you hear 2 to 3 mm per 24 hours. A normal bathroom joint can often take light wetting after a day; full cure takes longer. That is not a promise for every cartridge.

When to wait and when to rip it out

Wait at 10–15 °C: it simply goes slower. Raise the humidity a little if you are in a new build with dehumidifiers roaring: silicone needs water vapour. Warm the room towards 18–20 °C if you sealed near 5 °C.

Do not wait if it is still liquid or extremely tacky at 72 hours. At four days, it comes out. Do not use a hairdryer: heat does not cure it properly and can spoil adhesion.

Poke with a cocktail stick. Hard skin and a liquid core in a fat bead: sometimes only geometry and patience. The whole mass soft: cartridge or climate.

The cartridge and the depth

Check the date, often on the skirt or the nozzle. At 12–18 months, even unopened, the cross-linkers tire. Paste comes out, but the molecules will not join. If oil appears before the mass, it is dead.

With no backer rod, a deep meeting never sees air at the core. Months of paste in the middle, and three-sided adhesion as well.

How to do it again

Take it all out. A scraper and a silicone remover for the greasy film; leftover residue makes the new bead fail too. Do not shoot over the tacky layer: a useless sandwich.

Fresh cartridge — I go back to OTTOSEAL S100 or S110 depending on the substrate — PE backer, clean faces. Keep cartridges at room temperature in winter; an ice-cold tube in a cold bathroom reacts poorly.

Mistakes

Washing-up liquid by the cupful when tooling: acids and dyes that leave the skin tacky and dirty. Neutral finisher.

Harsh bleach on silicone already in: sometimes it breaks the surface and leaves it soft. That is not a “clean”: it is a replacement.