How To Seal a Kitchen Splashback

How do you seal a kitchen splashback?

Sealing the splashback is the final step of installing one, and arguably the most important. If water gets behind the panel it creates mould and rot and traps dirt, none of which you can see until the damage is done. A bead of silicone along the joint between the splashback and the benchtop is what stops it.

The product is Selleys Wet Area Silicone, and the job takes about twenty minutes of work followed by 72 hours of curing. The two things that decide whether it looks professional are masking the joint before you start, and tooling the bead within the first few minutes.

What you need

• Selleys Wet Area Silicone
• A caulking gun
• Mineral turpentine
• Painters tape
• Clean cloth
• Spatula
• Scraper

Steps

1. Remove the old silicone using a sharp knife, then scrape away the residual silicone.
2. Clean and dry the surface with mineral turpentine.
3. Tape both sides of the gap before you begin sealing, to ensure a neat finish.
4. Cut the tip of the Selleys Wet Area Silicone cartridge, then cut the nozzle at a 45 degree angle.
5. Place the cartridge in the caulking gun and fit the nozzle.
6. With a steady hand, hold the gun at a 45 degree angle and carefully gun the sealant out, pushing it into the joint.
7. Smooth the sealant with a spatula dipped in detergent.
8. Remove the tape before the seal skins.
9. Clean up excess sealant before it skins, with a cloth dampened in mineral turpentine.
10. Allow 72 hours for the sealant to cure fully. You can then carefully trim any excess with a sharp blade.

Why each step matters

Removing all the old silicone. Fresh silicone does not bond well to cured silicone. A thin film left in the joint means the new bead is stuck to the old residue rather than to the benchtop and panel, and it will lift along that line. Where the residue is stubborn, Selleys Sealant Remover softens silicone, acrylic, SMP/hybrid and polyurethane sealants — spread at least a 5mm layer over the residue, leave it at least 10 minutes, then scrape.

Cleaning with mineral turps. The surface must be clean, dry and free of dirt, grease, oil and water. Turps lifts cooking oils and old cleaner residue and then flashes off without leaving anything behind, which is exactly what a silicone bond needs.

Taping both sides. This is the difference between a bead that looks like a professional laid it and one that does not. It also lets you tool more firmly, because any overrun ends up on the tape.

Cutting the nozzle at 45 degrees. Cut the opening to the width of the joint — smaller than you think, since you can widen it but not reverse it. The angle lets you hold the gun comfortably while keeping the tip in the joint.

Pushing the sealant into the joint. A bead laid on the surface has almost no depth of bond and will peel. One pressed into the gap grips both faces and can flex with the small movements a benchtop sees.

Tooling within 5 to 10 minutes. Selleys' directions specify tooling with a spatula dipped in detergent water within 5 to 10 minutes of application. The detergent stops the silicone dragging on the tool. After that window the surface starts to skin, and tooling tears it rather than smoothing it.

Removing the tape before the sealant skins. Leave the tape until the bead has skinned and you will pull the edge of the bead away with it.

The Wet Area Silicone figures

Technology	Neutral cure silicone, 100% silicone sealant
Tooling window	5–10 minutes after application
Full cure	72 hours
Guarantee	25 years against cracking and peeling (when used as directed, for private use, within 12 months of purchase)
Elongation at break	450% (ASTM D412)
Service temperature	-40°C to 150°C
VOC content	<50 g/L
Storage	Below 30°C; use within 6 months of opening

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

What the 72 hours means: the bead skins over long before that, but full cure — and therefore full waterproofing and full movement capability — takes three days. Avoid subjecting the seal to water pressure or movement until it has cured. In a kitchen that mostly means being careful about how you wash down the benchtop for the first few days.

What the 450% elongation means: the cured bead can stretch to several times its own width before breaking, which is why a silicone survives a joint that a rigid filler would crack in. A benchtop and a wall move relative to each other with temperature and load; the silicone absorbs it.

Neutral cure matters if the splashback or benchtop is stone. Neutral cure silicones do not release acid as they cure, which makes them the safer choice against natural and engineered stone and against mirror backing.

Which surfaces it works on

Selleys Wet Area Silicone works on ceramic, glazed and porcelain fixtures, metal, copper and brass fittings, powder coated aluminium, aluminium, plastic laminates, rubber, glass, stainless steel and concrete — which covers essentially every splashback and benchtop combination in a domestic kitchen.

Alternatives for particular cases: Selleys White For Life Silicone Sealant if you are sealing as part of the White For Life tiling system, and Selleys All Clear where you want a clear rather than white bead. Selleys Glass Silicone is the product for glass and window frames.

Limitations — where this sealant should NOT be used

• Not paintable. Complete any painting seven days before applying the sealant, not after.
• Not suitable for polypropylene, polyethylene or PTFE.
• Not suitable for aquariums.
• Not suitable for food or drinking water contact. This matters in a kitchen: seal the joint behind and beside the working surface, not anything that food sits directly on or that forms part of a drinking water system.
• Not suitable for permanent water immersion.
• Surfaces must be dry. Clean with turps and allow to dry completely — silicone will not bond reliably to a damp surface.

Safety: a splashback is the one joint with a burner behind it

The method above is a solvent method. Mineral turpentine cleans the surface, mineral turpentine cleans up the excess, and if the old bead needs softening there is a third solvent in the room. All of that happens at the exact spot where a gas cooktop sits. That is the connection worth making on this page.

Selleys Sealant Remover carries the signal word Danger: H304, may be fatal if swallowed and enters airways; H226, flammable liquid and vapour; H336, may cause drowsiness or dizziness; H315, causes skin irritation. It is Poison Schedule S5 and Dangerous Goods Class 3, UN 1133, Packing Group II.

Selleys All Clear, offered above as the clear-bead option, is also Danger: H225, highly flammable liquid and vapour, with H315 and H319, and the same Class 3, UN 1133, Packing Group II transport entry — the same as a solvent contact adhesive, in a sealant cartridge.

What follows for this job. Before you start, turn the cooktop off at the wall and confirm there is no pilot alight. Open a window. Do not relight anything until the turps has flashed off and the room has cleared — H225 and H226 vapour is heavier than air, so it sits on the benchtop and runs down towards the floor rather than drifting out the window. A range hood pulling over a live burner is not ventilation in this situation.

H304 has one consequence that differs from everything else here: if it is swallowed, do not induce vomiting. The hazard is the liquid being drawn into the lungs. Keep it in its own container, never decanted, and off a bench where food and drink are.

Wet Area Silicone itself is the mild one — signal word Warning, with H319 (serious eye irritation) and H317 (may cause an allergic skin reaction). H317 is the reason the method above says to tool with a spatula dipped in detergent rather than a wet finger. Sensitisation is not irritation that washes off: it is permanent once acquired, and it is built by repeated casual contact over many jobs. The detergent is there for the finish; the spatula is doing something else.

The lower-hazard choice, where the job allows it. Wet Area Silicone carries no flammability classification. If the joint you are sealing sits directly behind a gas cooktop, that is a reason to prefer it over All Clear unless a clear bead is genuinely required — and where the old bead can be cut and scraped away, skipping the Sealant Remover removes the H304 and H226 exposure entirely.

Poisons Information Centre — 131 126 in Australia, 0800 764 766 in New Zealand.

Common questions about sealing a kitchen splashback

How long does the sealant take to cure?

72 hours for a full cure. It skins over much sooner, but leave it undisturbed for the full three days.

Can I put new silicone over the old bead?

No. Remove the old silicone completely with a sharp knife and scrape away the residue, or soften it with Selleys Sealant Remover. Fresh silicone does not bond well to cured silicone.

How do I get a neat line?

Tape both sides of the gap before you start, tool the bead with a spatula dipped in detergent, and remove the tape before the sealant skins.

How long do I have to smooth the bead?

Five to ten minutes from application. After that the surface begins to skin and tooling will tear it.

What do I clean the surface with first?

Mineral turpentine, then let it dry completely. The joint must be free of dirt, grease, oil and water.

What angle do I cut the nozzle at?

45 degrees, sized to the width of the joint. Cut small first — you can always open it up.

How do I clean up the excess?

A cloth dampened in mineral turpentine, before the product skins. Once cured, trim carefully with a sharp blade.

Can I paint over the sealant afterwards?

No. Wet Area Silicone is not paintable, so any painting has to be done seven days before you seal.

Which silicone for a stone benchtop?

A neutral cure silicone — Selleys Wet Area Silicone is neutral cure, so it does not release acid as it cures.

Will it stick to my laminate benchtop?

Yes, plastic laminates are among its listed surfaces, along with stainless steel, glass, ceramic, porcelain and concrete.

How long does an opened cartridge last?

Store below 30°C and use within six months of opening.

What if I need to seal a joint that is genuinely wet all the time?

This product is not for permanent water immersion. For sealing and bonding above or below the waterline in pools and spas, Selleys Marine Flex is the specialist product.