How To Clean Sealant Left in the Nozzle

How do you clean away the sealant left in the nozzle after use?

With almost all cartridge-type products the best approach is counter-intuitive: don't clean it out at all. Leave the nozzle screwed onto the cartridge with a little bit of product squeezed out of the end. That squeezed-out bead cures and forms a plug, which seals the main cartridge. Next time you want to use the product, the plug pulls out.

Over time the product may cure further down into the nozzle. When that happens you should be able to unscrew the nozzle, dig the hardened sealant out, and keep using the nozzle. Once any cartridge or tube of sealant is opened it has a limited useable life before it cures in the container and becomes unusable — but the technique above will let you use it for considerably longer.

Why the plug works

Silicone and hybrid sealants cure by reacting with moisture in the air. That is stated plainly in the technical data sheets: Selleys Roof & Gutter Silicone "requires atmospheric moisture to cure", and the same applies to No Mould, Wet Area Silicone, 650 FC and the polyurethane sealants.

That is the whole mechanism. The enemy is not dirt in the nozzle — it is air reaching the product. A cured plug in the tip is an airtight seal made of the sealant itself, which is why it protects the cartridge better than a cap, a nail, or a screw pushed into the opening.

Scraping the nozzle clean after use does the opposite of what you want. It leaves an open passage from the outside air down to the body of the sealant, and the reaction simply works its way inward from there.

The method, step by step

Finish the job and release the pressure on the caulking gun so the cartridge stops extruding.
Leave the nozzle screwed on and fully tightened. A loose nozzle lets air past the cartridge thread, which is the second-most-common way an opened cartridge goes off.
Squeeze a small dag of sealant out of the tip — enough to sit proud of the opening. Do not wipe it off.
Stand the cartridge upright and leave the dag to cure. Cure times vary by product; a silicone skins in minutes and hardens over hours.
Next time, pull carefully on the hardened plug. It should come away leaving a clear nozzle ready to extrude.

When the plug breaks off or the product has cured deeper

This happens if the cartridge has sat for a long stretch, or if the plug was too small to grip.

Unscrew the nozzle from the cartridge.
Clear the nozzle out — a piece of wire or a small screwdriver works, pushed through from the wide end.
Dig any hardened sealant out of the cartridge opening as well.
Re-attach the nozzle and extrude a little onto scrap material to check the flow is smooth and even before you go back to the joint.

If the cured section runs deep into the cartridge itself rather than just the nozzle, that cartridge has reached the end of its useable life. There is no way to reverse a cured silicone.

Cleaning wet sealant off the nozzle, gun and hands

This is a different question and the answer comes straight from the technical data sheets: it depends on the chemistry.

Silicone sealants — No Mould, Wet Area Silicone, Glass Silicone, Roof & Gutter, Brick & Concrete: uncured product may be removed with mineral turpentine. Cured product has to be removed with Selleys Sealant Remover or by cutting and scraping.
Hybrid and polyurethane sealants — 650 FC and the ProSeries Flexiseal range: spills and tools clean up with mineral turps before the product cures. Cured product can only be removed mechanically.
Water-based fillers — No More Gaps Exterior: clean up excess with water using a damp cloth before it dries. Cured caulk has to be cut, and the remainder can be softened with acetone.
All Clear: uncured product with mineral turpentine; cured product by cutting and scraping.

In every case the instruction is the same in spirit — clean up before the product skins. A minute with a turps rag while the sealant is still wet saves a great deal of scraping later.

Storing the cartridge between uses

The plug protects the cartridge from air. Storage conditions protect it from heat, and the published limits are tighter than most people assume.

Glass Silicone: store in a dry place below 30°C; after opening, use within 6 months.
Wet Area Matt Silicone: store in a dry place below 30°C; use within 6 months of opening.
Silicone 401: store unopened below 27°C in a dry area; use within 12 months of purchase.
Roof & Gutter Silicone: store unopened below 27°C, out of direct sunlight; best used within 12 months of manufacture.
650 FC: store unopened below 30°C in a cool dry place away from direct sunlight; 12 months from date of manufacture.

A cartridge left in the sun on the back of a ute, or in a shed roof space over summer, is well past these limits. That does more damage than a poorly plugged nozzle.

Safety: for one product on this page, storage is not just a shelf-life question

The storage limits above are mostly about keeping a cartridge usable. For one product in the clean-up list they are also a safety control.

Selleys Sealant Remover, named here for cured silicone, is classified Danger, Poison Schedule S5, and is more than 60% petroleum naphtha:

H304 — may be fatal if swallowed and enters airways (aspiration hazard, Category 1)
H226 — flammable liquid and vapour; Dangerous Goods Class 3, UN 1133, Packing Group II
H336 — may cause drowsiness or dizziness
H315 — causes skin irritation

Read this page's closing point again with that in mind. A cartridge left in the sun on the back of a ute, or in a shed roof space over summer, costs you a cartridge. A 375g tub of Class 3 flammable paste in the same place is a different matter: keep it away from heat, sparks and direct sunlight, off the ute tray in summer, and out of a roof space. Packing Group II is the middle rung of Class 3, not a nominal rating.

H304 is the reason storage height matters as much as storage temperature. It is a light beige paste in a screw-top tub that looks like filler, and it lives in the same drawer or bucket as the caulking gun and the half-used cartridges. Lid on, stored high, out of reach of children, and never decanted into another container. If any is swallowed, do not induce vomiting — that is the mechanism that gets a light hydrocarbon into the lungs. Rinse the mouth, give a glass of water and seek medical advice immediately.

The mineral turpentine this page recommends for uncured silicone, hybrid and polyurethane product is also a flammable solvent, and gets the same storage treatment.

The cartridges themselves are a much lower rung, with one statement worth knowing. Roof & Gutter Silicone and Wet Area Silicone are classified Warning, with H319 (causes serious eye irritation) and H317 (may cause an allergic skin reaction). H317 is skin sensitisation rather than irritation: permanent once acquired, then triggered by far smaller exposures, and built by repeated casual contact. Pulling cured plugs out of nozzles and digging sealant out of cartridge openings with bare fingers, cartridge after cartridge, is precisely that kind of contact. Wear gloves for it, and note that the cured plug itself is inert — it is the soft material behind it that is not.

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

Common questions about sealant left in the nozzle

Should I cut the plug off or pull it out?

Pull it out. Cutting the nozzle back shortens it each time and eventually widens the opening past the bead size you want.

Can I put a nail or screw in the nozzle instead?

Selleys' advice is the cured plug. A nail leaves an air path around it, and the product cures around the nail rather than sealing itself.

Do I need a new nozzle every time?

No. Unscrew it, clear the hardened sealant out with wire or a small screwdriver, and re-attach it.

How long will an opened cartridge last?

It has a limited useable life once opened, and the published figure varies by product — 6 months after opening for Glass Silicone and Wet Area Matt Silicone, for example. The plug technique extends the practical life; it does not remove the limit.

Why does the first bit out of the nozzle look lumpy?

Opened cartridges may skin and form a lump near the opening. Discard the lumps and skin, then use the remaining product — that is the instruction in the 650 FC and Roof & Gutter technical data sheets. Extrude a little onto scrap first to check the flow.

Does the same approach work for tubes as well as cartridges?

Yes for cartridge-type products generally. For the squeeze tubes, replace the cap after use — the Instant Gasket directions add that you should let the sealant cure in the nozzle and remove it before the next use, which is the same principle.

Can I store a part-used cartridge in the freezer or fridge?

The technical data sheets specify cool, dry storage below a stated temperature and nothing beyond that. Stick to what they say rather than improvising.

What is the best way to store an opened tube overall?

The plug plus a tightly screwed nozzle, stored cool and dry. That is covered in more detail in how to store sealant.

How do I clean sealant left in the nozzle before it cures?

For fresh, uncured sealant, clean the nozzle before the sealant cures by using mineral turpentine to dissolve and remove the wet product from the nozzle and application tools. This should be done promptly to prevent the sealant from hardening in place.

How do I clean a sausage gun nozzle after using sealant?

For a sausage gun, nozzle cleaning can be done by inverting the can and spraying until clear propellant comes out, or by soaking the nozzles in turps to remove residual material effectively.

What should I do with the nozzle after finishing a sealant cartridge?

The directions recommend allowing the sealant to cure in the nozzle and removing it before the next use, which prevents buildup and keeps the nozzle functional for future applications.

Can I remove sealant from a nozzle once it has already cured?

Yes, but it's more challenging—cured sealant can only be removed mechanically, such as by scraping or cutting with a blade, since chemical solvents are less effective once the material has fully cured.

What is the best way to prevent sealant buildup in a nozzle?

The best practice is to clean nozzles immediately after finishing your application work, before the sealant has time to skin over and cure, which ensures easier cleanup and extends the life of your application tools.