3C Polymer Sealant Review

Updated Apr 6, 2023 | Posted Mar 25, 2023 | Product Review, Sundries | 1 comment

3C Polymer Sealant is an adhesive, silicone and Decorators’ caulk in one product. It can be used internally or externally on substrates like timber, masonry, plaster, and uPVC. It uses a new type of technology, meaning 3C Polymer Sealant can perform well on a multitude of tasks, but contains absolutely no oil. This also means 3C Polymer Sealant is fully over-paintable.


My 3C Polymer Sealant Review


A few months ago I was given a tube of 3C Polymer Sealant to try on some problem areas on a hall, stairs and landing. These were the kind of internal cracks that always have slight movement such as the main wall stringer and some timber underneath a second stairwell leading to another floor.

This was the perfect test for 3C Polymer Sealant as these cracks are usually a nightmare to fix. I would normally dig the crack out, seal any loose material, fill flush with flexible Toupret filler, then go over with some CT1.

Could I fill these same cracks with a quick squirt of 3C Polymer Sealant? That would certainly save me some time. I needed something that would grip, fill the gap, remain flexible, and then be paintable afterward.

Applying 3C Polymer Sealant feels like applying caulk, although it has a much denser and heavier consistency, and a slight chemical smell. It dries with a little sheen and fesls like a very hard rubber to the touch. There is no shrinkage or slumping.


Available online, it is a far easier product to work with than either grip fill, or normal silicone. It isn’t as messy either, just use it as you’d normally use caulk and you can’t go wrong.

I ended up applying a thick bead of 3C Polymer Sealant in some areas, so I was worried about how well the paint was going to take to it. I went straight on with two coats of water-based satinwood the next day. The paint took brilliantly! No crazing, no flashing, no adhesion issues.

I left this review for a few months because I wanted to check how it performed. I went back today and not one part of it has failed. Yes, it’s more expensive than caulk, but it probably saved me 2 hours work and I didn’t need multiple products.

As a professional Decorator, I have now switched from caulk to 3C Polymer Sealant for a lot of my jobs. I know it’s more expensive, but I also know it isn’t going to fail on me.

Click here to see current prices.

3C Polymer Sealant Review – by Lee Thornton

Updated Apr 6, 2023 | Posted Mar 25, 2023 | 1 comment

1 Comment

  1. Phil

    Good review, lot’s of these hybrid sealants and gap fillers now. It seems to be the way forward but would be interesting to know if you can coat it while still wet like Isomastic or HB.


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