Sealant Substrate Compatibility Guide: Which Sealant Works on Glass, Stone, Metal, Concrete and Plastics?

Quick answer: No single sealant suits every substrate. Neutral oxime-cure silicones are the safest general choice for glass, aluminium and most metals; natural stone requires a dedicated non-staining, plasticiser-free stone sealant; and MS (modified silane) sealants offer the widest compatibility across porous and painted surfaces — plus they can be overpainted, which silicones cannot. The full compatibility matrix below covers five sealant types across 20+ common construction substrates.

How do I read this compatibility chart?

A "✗" does not always mean the sealant will physically fail on that substrate. In several cases it means the product is not designed for that application — for example, a stone-specific sealant is formulated for stone cladding joints, not glazing, even though silicone chemistry bonds well to glass. Where this distinction matters, it is noted below.

Substrate compatibility matrix (5 sealant types × 20+ substrates)

The five product types compared:

1. GP Silicone (Oxime) — general-purpose neutral-cure silicone
2. Weather Seal 25 — ±25% movement weather-resistant silicone (oxime-cure)
3. Stone Seal 25 — ±25% movement non-staining stone-specific silicone (oxime-cure)
4. Curtain Wall 35 — ±35% movement high-rise curtain wall silicone (oxime-cure)
5. MS Silane — MS modified silane polymer sealant (silicone-free)

Glass & Aluminium

¹ For coated glass and factory-coated aluminium (PVDF / fluorocarbon), a project-specific adhesion test is recommended before application — coated surfaces vary significantly between manufacturers.

Natural & Engineered Stone

² On porous natural stone, standard silicones carry a risk of edge staining caused by plasticiser or silicone fluid migration. For visible stone joints, a dedicated plasticiser-free stone sealant is the industry-standard choice. If a general-purpose silicone must be used, conduct both adhesion and stain testing first.

Concrete & Masonry

Metals

Plastics & Composites

³ PP and PE are low-surface-energy (non-polar) plastics that are inherently difficult for any sealant to bond. Surface treatment (e.g. priming or flame/corona treatment) plus adhesion testing is recommended regardless of sealant type.

Timber & Others

Which sealant should I use on glass and aluminium curtain walls?

For standard glazing and aluminium framing, a neutral oxime-cure silicone is the conventional choice: it is non-corrosive to metals and bonds reliably to glass and anodised aluminium without primer. For curtain wall weather seals, movement capability is the deciding factor — joints subject to large thermal movement on high-rise façades call for a ±35% movement-grade sealant (compliant with GB/T 14683), while ±25% grades cover most standard expansion joints.

Two caveats apply. First, coated (low-E) glass surfaces vary between glass manufacturers, so run an adhesion test before specifying. Second, weather sealants are not structural sealants — structural glazing requires a separately certified structural silicone.

What sealant is safe for natural stone like marble and granite?

Use a plasticiser-free, non-staining stone-specific sealant. Porous stones (marble, limestone, sandstone, and to a lesser degree granite) can develop yellowing or oily edge stains when silicone fluids or plasticisers migrate from a standard sealant into the stone. A stone-grade formulation eliminates the migration source.

Three practical rules for stone joints:

• Never use acetoxy (acid-cure) silicone on natural stone or marble — the acetic acid released during cure can corrode calcareous stone surfaces. Neutral-cure chemistry (oxime or alkoxy) is the baseline requirement.
• High-movement curtain wall silicones are generally not formulated for stone and carry staining risk on visible stone joints — check the product's stone-compatibility statement before use.
• MS silane sealants are a viable alternative for stone where paintability or lower staining risk is desired, though for premium visible stonework a dedicated stone silicone remains the standard specification.

When should I choose an MS (modified silane) sealant instead of silicone?

Choose MS sealant when the joint needs any of the following:

• Overpainting — MS polymers accept paint after cure; silicones do not, and silicone residues can cause paint dewetting (fisheyes) on surrounding surfaces.
• Porous substrates without primer — MS adheres strongly to timber, concrete and masonry, typically without priming.
• Low odour / solvent-free application — relevant for occupied interiors.
• Silicone-free zones — e.g. workshops that later apply coatings, where silicone contamination is a process risk.

Silicone remains the stronger choice for sustained UV exposure, the highest movement classes, and glazing applications — weather-grade silicones typically offer the longest exterior service life (25+ years for high-grade curtain wall products).

Why does the stone sealant show "✗" on glass and metal?

This is a design-scope marking, not a failure prediction. Stone-specific silicone bonds adequately to glass and metal in chemical terms, but it is formulated and tested for stone cladding joints — its performance envelope (movement accommodation, weathering, certification scope) is defined for that application. Using it for glazing or curtain wall weather seals would mean operating outside its tested scope. The same logic applies in reverse: curtain wall silicone on stone joints is marked ✗ primarily because of staining risk on stone, not bonding failure.

Do I always need a primer on porous substrates?

For standard silicones on concrete, masonry, brick and timber: usually yes — a primer significantly improves long-term adhesion on porous, dusty or alkaline surfaces, which is why these cells are marked △.

For MS silane sealants: usually no — good adhesion to porous substrates without primer is one of the chemistry's defining strengths. Exceptions exist (constantly wet joints, very friable surfaces), so for critical joints an adhesion test remains good practice.

FAQ

Q: Can I use the same sealant for glass, aluminium and stone on one façade project? A: Usually not. Glass and aluminium joints take a weather-grade silicone, while visible stone joints need a non-staining stone-specific sealant. Specifying two products per façade is normal industry practice.

Q: What does ±25% or ±35% movement capability mean? A: It is the joint movement the cured sealant can repeatedly accommodate as a percentage of original joint width. A 20 mm joint sealed with a ±25% product can cycle between 15 mm and 25 mm. Higher-movement façades (high-rise curtain walls, long aluminium panels) typically specify ±35%.

Q: Is oxime-cure silicone acidic or neutral? A: Neutral. Oxime-cure is a neutral-cure chemistry — unlike acetoxy (acid-cure) silicone, it does not release acetic acid and is non-corrosive to copper, marble, concrete and coated surfaces.

Q: Why did my sealant stain the marble around the joint? A: The most common cause is migration of plasticisers or silicone fluids from a standard sealant into the porous stone, appearing as darkened or oily joint edges. Prevention: use a plasticiser-free stone-grade sealant on natural stone.

Q: Can MS sealant be painted over? A: Yes — MS modified silane sealants are paintable after full cure, and being silicone-free they can also be applied over most existing coatings without compatibility issues. Always confirm paint compatibility on a small area first.

Q: Are these compatibility ratings a guarantee? A: No. Substrate coatings, surface condition and site environment vary widely. The matrix reflects typical performance; for any critical or unusual application, conduct a project-specific adhesion test or consult technical support.

The compatibility information above is provided for reference. Adhesion testing is recommended before use on coated, painted or unusual substrates. For special applications and project-specific specifications, contact our technical support team.