How to calculate sealant quantity for a joint
Width × depth × length gives you millilitres. Divide by the pack size, add waste and round up.
Sealant guides
How to choose, apply and fix sealants: wet areas, glazing, fire-rated joints, joint design, cure times and quantities.
Joint design
When should you use backer rod with sealant?
What backer rod does, when a joint needs it, how to size it, and when bond-breaker tape is the better choice.
Sealant joint design basics: movement, depth and backing
How wide and deep a sealant joint should be, why it must stick to two sides and not three, and where backer rod comes in.
Technical basics
Sealant vs caulk vs adhesive: what is the difference?
Caulk fills gaps for paint. Sealant keeps water out of joints that move. Adhesive holds things up.
Sealant FAQ
Short answers to the questions we hear most: which sealant to use, painting, mould, curing, backer rod, shelf life and fire rating.
Neutral-cure vs acetoxy silicone: what's the difference?
Acetoxy silicone smells of vinegar and can attack some metals and stone. Neutral cure doesn't. Here's which one to use where.
Inspection & maintenance
How to inspect and maintain exterior sealant joints
What to look for on a walk-round, what each kind of failure means, and when to patch or replace the run.
How to store sealant and check an expired cartridge
Shelf life and storage temperatures for each Pereseal product, and how to tell when a pack has gone off.
Documents & specification
How to check a fire-rated sealant system
A fire rating belongs to the tested joint, not the cartridge. How to match your joint to the Pereseal FR test.
How to test sealant adhesion and compatibility
A simple pull test on the real surface, the combinations to rule out first, and how to check stone for staining.
How to read a sealant technical data sheet
What to look at first on a TDS, what the numbers mean, and which documents you need alongside it.
Wet areas
Why does bathroom silicone turn black?
It’s mould on a joint that stays damp. When to clean it, when to cut it out, and how to stop it coming back.
How to remove and replace bathroom silicone
Cut out the old bead, clean and dry the joint, reseal with an anti-fungal silicone and keep the water off it. Step by step.
How to choose sealant for bathrooms and kitchens
Use a neutral-cure anti-fungal silicone for anything that gets wet. Here's why, where it doesn't belong, and what else matters.
Troubleshooting
Can you paint over sealant without the paint cracking?
Acrylic takes paint, silicone doesn’t. When to paint, and why paint cracks over a joint that moves.
Why sealant joints fail, and what the failure tells you
Peeled off one side, split down the middle or took the surface with it: each failure has a different cause and a different fix.
Choosing a sealant
Silicone vs polyurethane vs hybrid sealant
How the three compare on sun, paint, movement and bonding, and which one suits which joint.
Acrylic vs silicone sealant: which should you use?
Acrylic for gaps you want to paint. Silicone for joints that get wet, face the weather or move. The details, with the Pereseal product for each.
Application technique
How long does sealant take to cure?
Skin time, tack-free time and full cure are three different things. Here are the numbers for each Pereseal sealant and what slows them down.
How to apply sealant: preparation, gunning and tooling
Prepare the joint, fit backer rod, gun one continuous bead, tool it before it skins and protect it while it cures.