Short answer
Use acrylic, such as Pereseal 702, for gaps you want to paint, where the joint moves only a little. Use silicone where the joint gets wet, faces the weather or moves a lot. Silicone can't be painted, and acrylic shouldn't sit in water.
Both come in the same cartridges and both fill gaps, so they look interchangeable. They aren't. Pick the wrong one and you get paint peeling off a silicone bead, or an acrylic joint cracking round a shower tray.
How they differ
Acrylic (Pereseal 702)
- Paintable once dry
- Takes ±15% movement
- Dries as its water evaporates; tools and cleans up easily
- Can go onto damp (not wet) surfaces; no primer on most porous materials
- Joints 5–50 mm wide
- Needs 24 hours before water; not for joints that sit in water
Silicone (Pereseal AF, N, 802, MP)
- Can't be painted
- Takes ±25% to ±30% movement
- Waterproof and UV-resistant once cured
- Needs clean, dry surfaces
- Joints up to 30 mm wide
When to use acrylic
Use Pereseal 702 for skirting boards, cornices, architraves, door and window frames inside, cracks in plaster and gypsum board, and air-conditioning ducting. It's the one to use before painting. It also dampens sound through partition joints. It's weather-resistant enough for exterior caulking where the joint barely moves, but silicone lasts longer on a joint that works in sun and rain.
For fire-rated joints there's Pereseal FR, an intumescent acrylic that is also paintable. It's rated up to 4 hours to BS 476 Part 20.
When to use silicone
- Bathrooms and kitchens: Pereseal AF, anti-fungal, neutral cure.
- Windows, exterior joints, concrete and stone: Pereseal N, weatherproof, neutral cure.
- Glass and metal glazing: Pereseal 802, acetoxy, ASTM C920 Class 25.
- General sealing on non-porous surfaces: Pereseal MP, acetoxy.
Acetoxy and neutral cure suit different surfaces. Read neutral-cure vs acetoxy before you choose between them.
If the joint has to be painted
Only acrylic. Paint won't hold on silicone. The AF and N data sheets exclude paint coatings outright. Let the acrylic dry through before painting, and use a flexible paint on a joint that moves. More in can you paint over sealant.
Quick pick
Gap you'll paint, indoors
Pereseal 702 acrylic.
Bath, shower, basin or sink
Pereseal AF silicone.
Window perimeter or exterior joint
Pereseal N silicone.
Glass and aluminium glazing
Pereseal 802 silicone.
Fire-rated wall or floor joint
Pereseal FR fire-rated acrylic.
Still not sure?
Tell us the two surfaces and where the joint is. We'll tell you whether it's acrylic or silicone, and which one.
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