What is Selleys Glass Silicone, and where should you use it?

Selleys Glass Silicone is an acetic acid curing 100% silicone with excellent adhesion to glass, especially formulated for glazing and aquarium construction. It provides a durable waterproof seal, is UV and weather resistant, and carries a 25 year guarantee against cracking, crumbling or peeling away.

The single most important thing to know before you buy it is that acetic cure is what makes it excellent on glass and what rules out a long list of other substrates. It releases acetic acid as it cures — the sharp vinegar smell over the first day — and that acid corrodes some materials. It is not recommended for concrete, cement products, zinc or metals containing copper, and it is not suitable for roofs and gutters, where it will cause corrosion. Check the limitations section before you start, not after.

Technical specification

Property	Typical result
Technology	Acetic cure silicone sealant, 100% silicone
Curing rate	2mm per day
Skin time	5–10 minutes (weather dependent)
Full cure	72 hours
Elongation (ASTM D412)	Approx. 400%
Service temperature	Permanent −60°C to +150°C
Joint movement capability	±25%
Maximum sealant depth in a joint	10mm
Aquarium cure before use	7 days
Packaging	75g tube (clear) and 310g cartridge (clear)

These are indicative data only, not intended for the preparation of specifications.

What the key numbers mean in practice

Skin time of 5–10 minutes is very short, and it dictates how you work. Everything you intend to do to the bead — tooling, pulling masking tape, wiping a smear — has to happen inside that window, and it is weather dependent, so treat five minutes as the planning figure on a warm day. Run and tool a length you can finish rather than laying out a whole window before you pick up the spatula.

A curing rate of 2mm per day is why the depth limit exists. Silicone cures inward from the surface, so a bead deeper than about 10mm has a core that stays uncured for a long time. Hence the manufacturer's instruction: the depth of the sealant should be no more than 10mm in joints. To fill larger joints, use a suitable backing rod — closed cell polyethylene foam or similar — leaving the gap depth no larger than half the width of the joint.

The 72-hour cure figure follows from the same arithmetic, and it is a minimum for a shallow bead. A deeper joint takes proportionally longer.

The 7-day aquarium cure is a separate and stricter requirement. A tank seal is under constant water pressure and lives with fish in it, so the sealant must be fully through-cured and the residues washed out. The instruction is: allow to cure for 7 days, then thoroughly wash out with water, drain and refill before introducing fish. Do not shortcut this.

±25% joint movement capability with approximately 400% elongation means the cured bead tolerates the joint widening or narrowing by a quarter of its width. That covers normal thermal movement in a window frame, provided the bead has depth in the joint rather than being wiped across the surface.

Where to use it

Glass Silicone is perfect for use on or around:

• Windows and window frames
• Glass aquariums (allow 7 days cure before use)
• Repairs in dryers, ovens, refrigerators and washing machines

It will bond to materials such as glass, glazed ceramics, porcelain, stainless steel, most woods, aluminium, many plastics including polystyrene, rubber and canvas. The wide service temperature range — permanent −60°C to +150°C — is what makes appliance repairs viable, covering both a freezer and an oven door.

For related glazing products, see the glass sealant range.

How to apply it

Use in a well ventilated area, and avoid contact with skin and eyes.

1. Clean and dry the surface using mineral turpentine, removing oil, dirt and grease. Silicone will not bond through a film of either.
2. Cut the tip off the cartridge and cut the nozzle at a 45° angle. Fit the nozzle to the cartridge and place the cartridge into a caulking gun.
3. Fit a backing rod for joints deeper than 10mm — closed cell polyethylene foam or similar — leaving the gap depth no larger than half the width of the joint.
4. Hold the caulking gun at a 45° angle and gun the sealant ahead of the nozzle, ensuring the product is pushed into the joint rather than laid across it.
5. Tool with a spatula dipped in soapy water for a smooth finish.
6. Clean up before the sealant skins in 5–10 minutes, with a cloth dampened in mineral turpentine.
7. Allow 72 hours to cure. At that point any unneeded sealant can be removed by trimming with a sharp blade — but avoid under-cutting the seal, which weakens the bead where it carries movement.

For neater joints, mask the sides before applying the sealant and remove the tape before the sealant skins. On a window that tape line is directly in view, so this is worth doing.

Limitations — where it should NOT be used

This is the section that matters most on an acetic cure silicone:

• Not recommended for use on concrete, cement products, zinc or metals containing copper.
• Not suitable for use on roofs and gutters, as it will cause corrosion. Use Selleys Roof and Gutter Silicone instead.
• Not for mirrors. Use Liquid Nails Mirror & Metal. The acid attacks the silvered backing on a mirror.
• Not paintable. Complete any painting seven days prior to applying the sealant.
• Not suitable for use on oily woods such as cypress, teak or cedar. The natural oils in those timbers prevent the silicone bonding.
• Not recommended for use in below waterline applications, glass aquariums excepted. Use Selleys MarineFlex for below waterline applications.
• Not for use on polyethylene, polypropylene or Teflon. Pre-test plastics before use.

The gutter warning deserves emphasis because the job looks so similar to a glazing job. A gutter is usually zinc-coated steel or contains copper somewhere in the run, and an acetic silicone will corrode it from the inside of the joint outward — a failure that appears months later as a leak in a seal that looked perfect when it was applied.

The aquarium exception to the below-waterline rule is genuine but narrow: suitable for constructing and repairing small aquariums. Specialist design is required for large tanks. Contact Selleys if you are unsure.

Clean up, storage and the guarantee

Uncured product may be removed with mineral turpentine. Cured product can be removed with Selleys Sealant Remover, or by cutting and scraping.

Store in a dry place below 30°C. After opening, the sealant should be used within 6 months.

The 25 year guarantee applies when the product is used as directed for private use and within 12 months of purchase, and covers crumbling, cracking or peeling away. If the product does not perform as specified within the relevant warranty period, Selleys will replace the goods free of charge; you must show proof of purchase and bear the expenses of making a claim. These benefits are in addition to rights and remedies under any applicable law, including the consumer guarantees under the Australian Consumer Law.

Hazard classification

Classified as hazardous under Safe Work Australia GHS 7, with the signal word Warning.

• Flammable liquids — Category 4. H227: combustible liquid.
• Eye irritation — Category 2A. H319: causes serious eye irritation.
• Skin sensitisation — Category 1. H317: may cause an allergic skin reaction.

What is in it

Chemical entity	CAS number	Proportion (w/w)
Acetoxysilane	4253-34-3	1–10%
Octamethylcyclotetrasiloxane (D4)	556-67-2	<1%
Non-hazardous or below reporting limits	—	Balance

The acetoxysilane content is the acetic cure system — it reacts with moisture in the air and releases acetic acid as it sets. That is the vinegar smell, and it is the whole reason for this product's substrate restrictions: acetic acid corrodes copper-bearing metals, zinc, and concrete and cement products, and attacks the silvered backing of a mirror.

What skin sensitisation means. It is not the same as irritation. Irritation is a local reaction that settles once contact stops. Sensitisation is the immune system learning to react to the material — and once that has happened it is generally permanent, it can be set off by much smaller exposures than the one that caused it, and the reaction tends to worsen with each subsequent contact rather than fade. It typically develops after repeated casual contact, not one dramatic exposure, which is exactly the pattern of smoothing beads with a wet finger job after job.

Wear gloves, and tool the bead with a tool or a soapy finger inside a glove rather than bare skin. Once fully cured the sealant is inert; the hazard belongs to the uncured material.

H227 combustible is a low-level flammability classification — it will burn if you set fire to it, but it is not a flammable liquid in the sense that a solvent adhesive is. Normal care around ignition sources is sufficient.

Protection

• Gloves — nitrile rubber for intermittent contact.
• Eye protection — safety glasses or goggles.
• Ventilation — work in a well-ventilated area; do not work in a confined space.
• Wash hands before eating, drinking or smoking, and wash contaminated clothing before reuse.

First aid

Exposure	What to do
Eyes	Rinse cautiously with water for several minutes, removing contact lenses if present and easy to do, then keep rinsing. If irritation persists, get medical advice.
Skin	Wash with soap and water. If a rash, redness or itching develops — including some hours later — get medical advice, as this may indicate an allergic reaction rather than simple irritation.
Inhalation	Move to fresh air. If irritation persists, seek medical advice.
Swallowed	Do not induce vomiting. Rinse the mouth and seek medical advice.

If poisoning occurs, contact a doctor or the Poisons Information Centre — 131 126 in Australia, 0800 764 766 in New Zealand — with the container to hand. Selleys emergency line: 1800 220 770 in Australia, 0800 220 770 in New Zealand.

Common questions about Selleys Glass Silicone

Can I use it to build an aquarium?

Yes, for constructing and repairing small aquariums. Allow it to cure for 7 days, then thoroughly wash out with water, drain and refill before introducing fish. Large tanks require specialist design.

How long does it take to cure?

72 hours in normal use, at a rate of 2mm per day. Aquariums need 7 days.

How long do I have to tool the bead?

Five to ten minutes, weather dependent. That is the skin time, and all tooling and tape removal must happen before it.

How deep can the bead be?

No more than 10mm. For larger joints, use a backing rod such as closed cell polyethylene foam, leaving the gap depth no larger than half the width of the joint.

Can I use it on a mirror?

No. Use Liquid Nails Mirror & Metal instead.

Can I use it on gutters?

No. It will cause corrosion. Use Selleys Roof and Gutter Silicone.

Can I use it on metal?

Stainless steel and aluminium are listed among the materials it bonds to, but it is not recommended on zinc or metals containing copper.

Can I use it on concrete?

No — not recommended for concrete or cement products.

Can I use it on teak or cedar?

No. It is not suitable for oily woods such as cypress, teak or cedar.

Can I paint over it?

No. Complete any painting seven days before applying the sealant.

Will it survive oven temperatures?

Its permanent service temperature is −60°C to +150°C, and repairs in ovens are among its listed uses.

Will it stick to plastic?

Many plastics including polystyrene, but not polyethylene, polypropylene or Teflon. Pre-test plastics before use.

What sizes does it come in?

A 75g tube and a 310g cartridge, both clear.

How long does an opened cartridge last?

After opening, the sealant should be used within 6 months. Store below 30°C in a dry place.

How do I remove cured silicone?

With Selleys Sealant Remover, or by cutting and scraping.