What is Selleys Pro-Trade Gap Filler Fast Skin, and where should you use it?

Selleys Pro-Trade Gap Filler Fast Skin is a water-based acrylic gap sealant formulated with a quality polymer and high solid content for extremely low shrinkage and excellent resistance to paint cracking. It is a trade product, and the problem it is built around is the one that costs a painter a day: waiting for caulk before the first coat can go on.

It skins in 6 minutes and can be painted over in 10, with excellent adhesion to timber, plasterboard, masonry and aluminium. The trade-off is flexibility — movement capability is ±10%, so it belongs in joints where movement is modest. Selleys is specific that it should not be used on VJ, tongue and groove boards or weatherboard overlaps, because the flexibility is not sufficient for the movement expected there.

Technical specification

Property	Typical result
Technology	Water based acrylic
Colour	White
Density	Approx. 1.58
Application temperature	Above 10°C
Skin time (23°C / 50% RH)	6 minutes
Cure time	24–48 hours
Movement capability (ISO 9046)	±10%
Elongation	80%
VOC content	62 g/L (calculated per South Coast Air Quality Management District Rule 1168)
Coverage	Approx. 10.6 m per 300mL cartridge
Packaging	475 g cartridge, white

Indicative data only, not intended for the preparation of specifications.

Paint over times

Paint type	Paint over time
Gloss	10 minutes
Semi gloss	10 minutes
Low sheen	10 minutes
Flat	100 minutes
Ceiling	120 minutes

What the key numbers mean in practice

Skin time of 6 minutes governs how you work. On a trade job the temptation is to gun out a whole run and come back to tool it. Six minutes does not allow that. Apply a length you can smooth with a wet finger or damp cloth inside a few minutes, tool it, and move on.

The paint over table is the real value of the product, and it is not a single number. Gloss, semi gloss and low sheen all go on at 10 minutes. Flat needs 100 minutes and ceiling 120. Selleys explains why: paints with low binder content and high filler — flat and ceiling paints — have limited flexibility, and as the sealant cures and shrinks, that inflexible film cracks. If those paints are also applied too thickly, cracking can occur that has nothing to do with the sealant at all and everything to do with paint shrinkage.

Alkyd (oil-based) paints behave differently again. They have excellent paint crack resistance, but they restrict water loss from the sealant and so lengthen its cure time. If you are using an alkyd, Selleys recommends allowing longer cure times before painting, or taking care not to damage the integrity of the still-soft sealant. And on non-porous surfaces — aluminium window frames are the example given — allow full cure before painting, because the substrate cannot draw water out of the bead either.

For optimum paint crack resistance, filled gaps should not exceed 10mm width and 5mm depth. The effects of sealant shrinkage are more evident in larger gaps, giving low-binder paints a greater propensity to crack.

Cold and humidity both slow it down. The product takes longer to cure below 10°C and in high humidity — allow for longer cure times in those conditions, and note that the stated application temperature is above 10°C.

Where to use it

Pro-Trade Gap Filler Fast Skin is ideal where joint movement is expected and excellent paint crack resistance is desired. Typical applications:

• Gaps around ceiling cornices
• Door frames
• Window frames
• Skirting boards

It has excellent adhesion to timber, plasterboard, masonry and aluminium.

How to apply it

Surface preparation: ensure all surfaces are clean, dry and free of dust, grease, old sealant or flaking/powdery paint.

1. Cut the cartridge nipple, screw the nozzle onto the cartridge, and cut the nozzle at an angle to the bead size you want.
2. Apply using a caulking gun, forcing the sealant into the gap.
3. Smooth off with a wet finger or a damp cloth — within the 6 minute skin time.
4. Wait for the sealant to skin and strengthen. The directions specify 20 minutes; the paint over table allows gloss, semi gloss and low sheen at 10 minutes and flat and ceiling paints at 100 and 120 minutes respectively. Where the two differ, the longer wait costs you ten minutes and removes the risk.
5. Paint over with an acrylic or oil-based paint.

If the product is used in exterior applications, protect it from rain and other elements until it is painted.

Limitations — where it should not be used

• Do not use on VJ, tongue and groove boards, or weatherboard overlaps. The flexibility is not sufficient for the movement expected in those joints — Selleys directs you to No More Gaps Weatherboard instead.
• Not to be used outside if rain is imminent. Once applied it must be protected from rain until firmly skinned.
• Not suitable for permanent water immersion or constantly damp areas.
• Not suitable for joints with movement beyond ±10%, per the product page.
• Do not store below 0°C, and note that application temperature is above 10°C.

Clean up and storage

All tools can be cleaned up in water. Store in a cool dry place; the product should not be stored below 0°C.

Warnings, first aid and shipping information are on the product's Safety Data Sheet, available through the Selleys website.

Hazard classification

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

• Skin sensitisation — Category 1. H317: may cause an allergic skin reaction.

Not classified as Dangerous Goods by the criteria of the Australian Code for the Transport of Dangerous Goods by Road & Rail or of New Zealand NZS 5433.

What is in it

Chemical entity	CAS number	Proportion (w/w)
5-Chloro-2-methyl-4-isothiazolin-3-one (CMIT)	26172-55-4	<0.05%
2-Methyl-2H-isothiazol-3-one (MIT)	2682-20-4	<0.05%
Non-hazardous or below reporting limits	—	Balance

Two ingredients at under 0.05% each are the entire declared content of this product. CMIT and MIT are the preservative pair used to stop a water-based acrylic spoiling in the cartridge, and that chemical class is the one most commonly behind an H317 on a product of this type. The safety data sheet does not attribute the classification to a single ingredient, so read that as the likely explanation rather than a sourced one. The point worth taking from the table is that a sensitisation classification has nothing to do with how much of something is present — a trace of a potent sensitiser classifies a product exactly as a large quantity of a weak one would.

Sensitisation is not irritation. Irritation is a local reaction that settles once contact stops. Sensitisation is the immune system learning to react to the material: once it has happened it is generally permanent, it can afterwards be triggered by exposures far smaller than the one that caused it, and the reaction tends to worsen with each subsequent contact rather than fade.

This is a trade product, and that is exactly why the classification matters more here than it would on a consumer pack. Sensitisation is a cumulative hazard: it develops from repeated, unremarkable contact rather than from one bad exposure. The person who buys a twenty-pack of 475 g cartridges is, by definition, the person with the highest cumulative exposure to it. And a sensitivity acquired to these preservatives is unlikely to stay confined to this cartridge — the same chemical class is used widely across water-based fillers, sealants and paints, which makes it a trade problem rather than a product problem.

The directions above say to smooth off with a wet finger or a damp cloth inside the six-minute skin time. The safety data sheet's own precaution is to wear protective gloves and eye or face protection. Those two are easily reconciled: take the damp cloth option, or put a glove on the finger. On a job where you are tooling continuously to keep ahead of a six-minute skin, the difference between a cloth and a bare finger adds up quickly.

Protection

• Gloves — nitrile rubber is suitable for intermittent contact. Selleys notes that glove construction and local conditions vary, so the final assessment is the user's.
• Eye protection — safety glasses.
• Overalls and safety shoes where the job warrants them.
• Wash hands before smoking, eating, drinking or using the toilet, and wash contaminated clothing and protective equipment before storing or reusing it.

First aid

Exposure	What to do
Skin or hair	Effects may be delayed. Remove contaminated clothing and flush the skin and hair with running water; wash with plenty of soap and water. If a rash, swelling, redness or irritation develops — including hours later — seek medical advice, as it may be an allergic reaction rather than simple irritation.
Eyes	Wash out immediately with water. In any case of eye contamination it is a sensible precaution to get medical advice.
Inhalation	Move the person away from the exposure without putting yourself at risk. Loosen tight clothing, let them rest comfortably and keep them warm until fully recovered. Seek medical advice if effects persist.
Swallowed	Rinse the mouth with water. Do not induce vomiting. Give a glass of water to drink. Give nothing by mouth to an unconscious person. If vomiting occurs, give more water 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 Pro-Trade Gap Filler Fast Skin

How soon can I paint over it?

10 minutes for gloss, semi gloss and low sheen; 100 minutes for flat; 120 minutes for ceiling paint. The directions also give a 20 minute wait for the sealant to skin and strengthen before painting.

Why do flat and ceiling paints take so much longer?

They have low binder content and high filler, so the dried film has limited flexibility. As the sealant cures and shrinks, an inflexible film over it cracks.

What about oil-based paint?

Alkyd paints give excellent crack resistance but restrict water loss from the sealant, lengthening its cure time. Allow longer before painting, or take care not to damage the sealant while it is still soft.

Does the substrate matter?

Yes. On non-porous surfaces such as aluminium window frames, allow full cure before painting.

How long do I have to tool the bead?

Skin time is 6 minutes at 23°C and 50% relative humidity. Smooth with a wet finger or damp cloth inside that.

What is the maximum gap size?

For optimum paint crack resistance, filled gaps should not exceed 10mm width and 5mm depth.

Can I use it between weatherboards or on VJ boards?

No. The flexibility is not sufficient for the movement those joints see. Selleys directs you to No More Gaps Weatherboard for that application.

Can I use it outside?

Only with care. Do not use it outside if rain is imminent, and protect it from rain until firmly skinned. It is not suitable for permanent water immersion or constantly damp areas.

How long does it take to cure fully?

24 to 48 hours, and longer below 10°C or in high humidity.

How much movement will it take?

±10% by ISO 9046, with 80% elongation.

How much does a cartridge do?

The technical data sheet gives coverage of approximately 10.6 m per 300mL cartridge; the cartridge listed in its product information is 475 g.

How do I clean my tools?

All tools can be cleaned up in water.

For a smoother-tooling trade filler with a longer working window, see Pro Trade Gap Filler Smooth Finish; for large cavities, Pro Trade Expanding Foam. The full range is under gap fillers.