Most sealant questions start one level too low. Before you compare brands or grades, decide the chemistry — acid silicone, neutral silicone, MS polymer or polyurethane. The chemistry decides what the sealant will stick to, whether it will corrode the substrate, whether you can paint it, and how long the joint has to stay open before the next trade arrives. Only after that does the grade matter.
This guide puts the four families side by side, with the figures we actually publish. Where we do not publish a figure, the table says so rather than carrying a number we cannot stand behind.
Comparison table
| Property | Acid silicone | Neutral silicone | MS polymer | Polyurethane |
|---|---|---|---|---|
| Cure system | Acetic (releases acetic acid while curing) | Neutral, non-corrosive | Moisture cure, no isocyanates or solvents | Moisture cure, isocyanate-based |
| Skinning time | 5–20 min | 10–30 min | Specification on request | Not in our range |
| Full cure | 12–24 h (standard bead) | 24–72 h (depending on thickness) | Specification on request | Not in our range |
| Service temperature | −40 °C to +150 °C | −50 °C to +150 °C | Specification on request | Not in our range |
| Tensile strength | ≥1.0 MPa | ≥1.0–1.8 MPa | Specification on request | Not in our range |
| Elongation at break | ≥200–250% | ≥150–200% | Specification on request | Not in our range |
| Shore A hardness | 25–30 | 25–40 | Specification on request | Not in our range |
| Paintable | No | No | Yes | Yes |
| Safe on marble, granite, concrete | No — the acid attacks alkaline and porous substrates | Yes | Yes | Yes |
| Safe on mirror backing, galvanised metal | No | Yes | Yes | Yes |
| Typical use | Glass, glazing, shopfronts, aquariums | Facades, stone, curtain walls, structural glazing | Joints that must move and be painted | Structural bonding where strength beats weathering |
Acid silicone — fast, clear, and only for the right substrates
Acetic-cure silicone skins in 5 to 20 minutes and stays highly transparent, which is why it dominates glass work. The trade-off is in the name: while it cures it releases acetic acid. On glass, glazed tile, enamelled metal and most plastics that is harmless. On marble, granite, concrete, mortar, mirror backing and galvanised steel it is not — the acid stains porous stone and corrodes the reflective layer behind a mirror.
Our acid range runs from H568, which skins in 5–10 minutes for fast turnaround, to BY-808 for large panels and engineering projects. Full range: acid silicone sealants.
Neutral silicone — the default for facades and anything porous
Neutral cure removes the corrosion problem, so this is what goes on stone, concrete, aluminium panels and curtain walls. It skins slower (10–30 minutes) and takes 24–72 hours to cure through, and the range covers a wide span of strength: from HP-2000 for general weatherproofing up to HP-9900 at ≥1.8 MPa for structural glazing. Service temperature goes down to −50 °C, which matters in Central Asia and Siberia far more than it does in a catalogue.
For natural stone specifically there is a further requirement beyond neutral cure: the sealant must not migrate into the stone and leave a shadow along the joint. That is a separate, non-staining formulation — HP-5000, with ±25% movement capability. Full range: neutral silicone sealants.
MS polymer — when the joint has to move and be painted
Silane-modified polymers sit between the other two: roughly the movement capability of a silicone, with the paintability and low odour of a polyurethane, and without isocyanates or solvents. The practical reason to specify MS is simple — silicone cannot be painted. If the joint will be over-coated, silicone is ruled out no matter how good its other numbers are.
We have not published figures for our MS range yet. Rather than print numbers we cannot stand behind, we send the current datasheet directly — tell us the application and we will send the right one.
Polyurethane — and what we actually make instead
Polyurethane sealant is the choice when raw bond strength and abrasion resistance matter more than long-term weathering — expansion joints in concrete, industrial floors, vehicle bodies. It is paintable and tough, but it chalks under prolonged UV and it is isocyanate-based.
We do not currently produce a polyurethane sealant. What we do make in polyurethane is one-component foam — BY-101, BY-102 and BY-107, 65 to 80 litres of yield per can, applied from −20 °C to +50 °C. For the fixing jobs a polyurethane adhesive is often bought for, our nail-free adhesives cover the same ground: M1 carries up to 40–50 kg, M2 is moisture-curing with very high initial grab across mixed substrates.
How to choose, in one pass
- Glass to glass, glass to frame, shopfronts, aquariums → acid silicone. Fastest skin, clearest finish.
- Anything touching stone, concrete, mortar, mirror backing or galvanised steel → neutral silicone. The acid grade will stain or corrode it.
- Marble and granite facades → non-staining neutral silicone specifically, not just any neutral grade.
- The joint will be painted → MS polymer. Silicone is out, whatever else it offers.
- Interior joints and cracks that get filled and decorated → acrylic. Cheaper, paintable, not for permanently wet or moving joints.
- Filling a gap rather than sealing a joint → PU foam, not sealant at all.
Where the numbers come from
Every silicone figure above is the published range across our own grades, taken from the product datasheets and the printing on the cartridge. They are typical values, not a specification — always run a compatibility and adhesion test on the actual substrate before full application. Grade-by-grade figures sit on each product page.
Still not sure which chemistry the joint needs? Send the substrate, joint width and expected volume and we will name a grade — usually within 24 hours. Send an enquiry.
