What is Selleys Auto Fix Windscreen Sealant, and where should you use it?

Selleys Auto Fix Windscreen Sealant is designed to seal gaps around windows and windscreens to stop leaks quickly and effectively. It prevents the penetration of water, dust and drafts by forming a waterproof seal unaffected by vibration and temperature extremes, and the durable black silicone rubber seal is capable of withstanding joint movement of up to 25%.

The thing to understand before you choose it is what job it is actually for. This is a repair sealant for an existing windscreen rubber that has started to leak — you work the nozzle into the gap between the rubber and the glass and stop the leak there. It is a 100% neutral cure silicone, which is why painted surfaces appear among the materials it is listed for.

Technical specification

Property	Typical result
Technology	100% neutral cure silicone
Colour	Black
Density	1.02 g/ml
Application temperature	−20°C to 50°C
Skin time	5 minutes
Dry to touch / set time	30 minutes
Cure	24 hours
Shore A hardness (ASTM C661)	25
Elongation at break	370%
Movement capability (ASTM C719)	25%
Service temperature (ASTM C1246:2017)	−40°C to 180°C
VOC (USEPA Test Methods 24)	26 g/L
Packaging	100ml tube, black

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

What the key numbers mean in practice

The three timing figures describe three different states. The sealant skins in 5 minutes, dries to touch in 30 minutes, and cures in 24 hours. All smoothing has to happen inside the first five minutes. Dry to touch at 30 minutes means you can close the door without marking the bead — it does not mean the seal has developed its properties, so do not judge a repair by whether it holds a hose test half an hour in.

Joint movement capability of 25% is what makes this a vehicle sealant rather than a household one. A windscreen surround moves constantly: the body flexes over bumps, the glass and the frame expand at different rates between a cold morning and a hot afternoon, and the whole assembly vibrates while you drive. A 25% movement capability means the cured bead tolerates the gap widening or narrowing by a quarter of its width without tearing. Combined with 370% elongation at break, that is a seal designed to stretch rather than to hold rigid.

Shore A hardness of 25 is soft. That matters at a windscreen because a hard seal transmits body flex into the glass; a soft one absorbs it.

Note the difference between the −40°C to 180°C service temperature and the −20°C to 50°C application temperature. The first is what the cured seal survives; the second is the range you should be working in. A windscreen surround parked in summer sun is easily above 50°C, so move the car into shade before you start.

Where to use it

The manufacturer lists it for use on materials such as:

• Painted surfaces
• Rubber
• Glass
• Most plastics
• Metal

Note the important qualifier that sits alongside "rubber": the manufacturer's own limitation states the sealant did not adhere well to natural rubber, NBR and chloroprene/neoprene. Those are three specific named rubbers, and they are common ones. If your windscreen rubber is one of them, the sealant may not bond to it — read the limitations section below before you start rather than after.

For general sealing work on a vehicle or caravan rather than a window surround, the Auto Fix Auto Sealant is the versatile translucent product in the same auto sealant range.

How to apply it

Surface preparation first: clean the surface to leave no dirt and moisture. A leaking windscreen rubber usually has years of road grime packed into the gap, and silicone will not bond to any of it.

1. Remove any dirt or moisture between the rubber and the windscreen glass. Clean with mineral turpentine and dry.
2. Remove the cap, unscrew the nozzle and remove the seal. Replace the nozzle and cut it at a 45° angle.
3. If possible, insert the nozzle between the rubber and the glass, or the rubber and the metal. Squeeze the tube with steady pressure, ensuring the product is pushed into the joint, then smooth off with a gloved finger. Getting the nozzle inside the gap is the difference between sealing the leak path and laying a black line on top of it.
4. If further smoothing is required, smooth before the sealant skins — inside five minutes.
5. Clean up before the sealant cures, with mineral turpentine. Cured sealant can only be removed by scraping or cutting.
6. After use, replace the cap. Allow sealant to cure in the nozzle and remove it before the next use.

For neater joints, mask both sides before applying the sealant and remove the tape before the sealant skins. Tape pulled after skinning drags the edge of the bead with it — and on a windscreen, that edge is directly in the driver's line of sight.

Limitations — where it should NOT be used

• This sealant did not adhere well to natural rubber, NBR and chloroprene/neoprene.

That is the manufacturer's single stated limitation, and on this product it carries more weight than usual, because the surface you are most likely to apply it to is rubber. Natural rubber, NBR (nitrile) and neoprene are all used in vehicle seals and trim. Where the seal is one of those materials, expect the sealant to bond to the glass and the metal but not to the rubber itself — which may still stop a leak if the silicone bridges the gap, but is not a bonded repair.

Note also that the stated application temperature range is −20°C to 50°C. Working outside it is working outside the manufacturer's conditions.

Clean up and storage

Clean up before the sealant cures, using mineral turpentine. Once cured, it can only be removed by scraping or cutting — there is no solvent that will lift it off glass or paint later, so the wipe at the time is worth doing properly.

Store in a dry and cool place at a temperature below 30°C, and use within 24 months from the date of production. After use, replace the cap, let the sealant cure in the nozzle, and pull that plug out before the next job rather than trying to clear the nozzle immediately.

Hazard classification

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

• Eye damage/irritation — Category 2A. H319: causes serious eye irritation.
• Sensitisation — skin — Category 1. H317: may cause an allergic skin reaction.

It is not classified as Dangerous Goods by the criteria of the Australian Code for the Transport of Dangerous Goods by Road & Rail or New Zealand NZS5433.

What is in it

Chemical entity	CAS number	Proportion (w/w)
2-Butanone, O,O',O″-(methylsilylidyne)trioxime	22984-54-9	1–10%
2-Butanone, O,O',O″-(ethenylsilylidyne)trioxime	2224-33-1	1–10%
N-[3-(Trimethoxysilyl)propyl]ethylenediamine	1760-24-3	1–10%
Cyclotetrasiloxane, octamethyl-	556-67-2	<1%
Ingredients determined to be non-hazardous or below reporting limits	—	Balance

The two trioxime silanes are the crosslinkers of the 100% neutral cure system named at the top of this page, and oxime chemistry is the component class usually behind skin-sensitisation classifications in neutral cure silicones. That is the chemically obvious explanation for H317 rather than an attribution the safety data sheet makes, so treat it as reading rather than fact. Note also that the aminosilane at 1–10% is present at a markedly higher proportion here than in the other Auto Fix sealants, where it sits below 1%.

The sensitisation classification is the one that changes behaviour. It is not irritation: a sensitiser can teach your immune system to react to it, generally permanently once that has happened, with far smaller exposures sufficient to trigger it afterwards. It develops through repeated low-level contact, not one bad incident. This page tells you to smooth the bead with a gloved finger within the five-minute skin window — keep the glove on for that step every time, including the two-minute touch-up you did not plan for.

The working position is what makes H319 matter more here than the category alone suggests. Sealing around a windscreen or a door glass means working at head height with the nozzle pushed into a gap and your face directly alongside it, often with the tube squeezed hard to force product into the joint. If it lets go, it lets go towards your eyes. The safety data sheet's own eye first aid for this product is fifteen minutes of continuous flushing followed by transport to a doctor or hospital — not a rinse under the tap. Safety glasses are the proportionate response.

Protection

• Eye protection — safety glasses. Non-negotiable for work at or above head height.
• Gloves — nitrile rubber is suitable for intermittent contact.
• Ventilation — natural ventilation is adequate under normal use conditions. Open the doors if you are working inside the cabin.
• Overalls and safety shoes for workshop use; avoid contact with clothing.
• Wash hands before eating, drinking or smoking, and wash contaminated clothing before reuse.

First aid

Exposure	What to do
Eyes	Hold the eyelids apart and flush the eyes continuously with running water. Continue until advised to stop by the Poisons Information Centre or a doctor, or for at least 15 minutes, then transport to a doctor or hospital.
Skin	Effects may be delayed. Remove contaminated clothing and flush skin and hair with running water. If swelling, redness, blistering or irritation occurs, seek medical assistance.
Inhalation	Remove the person from exposure without becoming a casualty yourself. Loosen tight clothing, keep them comfortable, warm and at rest until recovered. Seek medical advice if effects persist.
Swallowed	Rinse the mouth with water. Do NOT induce vomiting. Give a glass of water. Never give anything by mouth to an unconscious person. 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 Auto Fix Windscreen Sealant

How long before I can drive the car?

It dries to touch in 30 minutes and cures in 24 hours. Handling is reasonable after 30 minutes; the seal reaches its full properties at 24 hours.

How long do I have to smooth the bead?

Five minutes — that is the skin time, and all smoothing must be finished before it skins.

Will it stick to my windscreen rubber?

Rubber is listed among the materials it is for, but the manufacturer states it did not adhere well to natural rubber, NBR or chloroprene/neoprene. Check what the seal is made of before you rely on a bond to it.

Can I use it on painted bodywork?

Painted surfaces are listed among the materials it is for, and it is a 100% neutral cure silicone.

What colour is it?

Black.

How do I actually get it into the leak?

If possible, insert the nozzle between the rubber and the glass, or the rubber and the metal, and squeeze with steady pressure so the product is pushed into the joint.

Will it survive car washes and rain?

It forms a waterproof seal that prevents the penetration of water, dust and drafts, and it is UV and weather resistant. Let it cure for 24 hours first.

Will vibration break the seal?

The seal is described as unaffected by vibration and temperature extremes, and it withstands joint movement of up to 25%.

What temperature can I apply it at?

Between −20°C and 50°C. A screen surround in direct sun can exceed that, so work in the shade.

How hot can the cured seal get?

Its service temperature is −40°C to 180°C.

What size does it come in?

A 100ml tube.

How do I get a tidy line?

Mask both sides before applying and remove the tape before the sealant skins.

How do I clean up, and how do I remove it later?

Mineral turpentine before it cures. Once cured, it can only be removed by scraping or cutting.