How do you store leftover paint, and how do you get rid of it?

Short answer: sealed, cool, off the floor and labelled

Good paint storage comes down to keeping air, heat and damp away from the paint. Here's the short version, pulled from the Dulux, Taubmans and Wattyl storage advice.

• Seal it. Wipe the rim clean, put plastic wrap over the opening and tap the lid on firmly. Taubmans says the plastic acts as an air seal and keeps the paint from drying out.
• Shrink the air gap. Dulux recommends moving unused paint into a smaller can, because the more air inside, the faster it will expire.
• Keep it cool and shaded. Taubmans says to store paint in a dry, cool place out of direct sunlight, and not to let it freeze.
• Get it off the floor. Dulux says to keep paint cans off the ground on a shelf.
• Stand it upright. Wattyl says to store tins upright in a cool, dry cupboard.
• Label it. Wattyl suggests the room, colour, brand, sheen, date and batch.

Store it badly and it won't keep. Taubmans says paint that isn't stored correctly may become lumpy or even rusty in a year or so.

How long paint lasts in the tin: years for water-based paint, if it's sealed and stored well

A sealed tin of water-based paint stored well lasts years, though none of the makers' pages we checked gives a fixed expiry date. Dulux says there's no strict timeframe for Wash&Wear in the can, because it depends on how and where the paint is stored. Here's what each maker says.

An opened tin follows the same rule. What shortens its life is the air left inside once some paint is gone. That's why Dulux suggests a smaller can and Wattyl suggests decanting touch-up amounts into an airtight container, since less air means longer life.

This is the paint in the tin. How long paint lasts once it's on the house is a different question, covered in our guide to how long exterior paint lasts.

How to seal a tin so the paint keeps

A tight seal keeps air out of the tin, and it only needs a bit of plastic and a mallet. Taubmans sets it out like this:

1. Clean the rim. Wipe away paint on the lip or rim of the can.
2. Cut a plastic circle. Cut plastic food wrap or a plastic grocery bag into a circle slightly bigger than the can.
3. Lay it over the opening. Put the plastic on top of the can before the lid goes back on.
4. Close it firmly. Tap the lid down with a rubber mallet, or tap lightly on a small block of wood with a hammer.

If there's only a little paint left in a big tin, move it. Dulux recommends transferring unused paint into a smaller can, and Wattyl suggests one of its Colour Sampler jars or any airtight container for touch-up amounts. A small jar is also easier to grab when a wall gets a scuff. Label the jar the same way you'd label the tin, because a jar of white paint with no name is hard to match later.

Hot garage or shed: fine on a shaded shelf, better in a cool cupboard

A garage or shed can hold paint, as long as the tins sit somewhere cool, dry and shaded. None of the Australian makers' pages we checked gives a top temperature. What they ask for is a dry, cool place out of direct sunlight (Taubmans), a cool, dry cupboard (Wattyl), and cans kept off the ground on a shelf (Dulux).

So on the Sunshine Coast, pick the coolest, shadiest spot you have. In a garage, that's a shelf off the slab, away from the roller door and away from any wall or window the sun hits. Keep tins clear of anything wet. If your garage or shed heats up badly in summer, a cupboard inside the house is closer to what the makers describe.

A garage that's filled up with old tins is a sign it's time to clear some out. Dulux's own advice on leftover paint says an excess of unused paint or empty cans can lead to a cluttered shed, garage or backyard. Keep what you'll use for touch-ups, and take the rest to a drop-off point (see below).

Label every tin before it goes on the shelf

A label turns a mystery tin into touch-up paint you can actually use. Wattyl suggests writing these on each tin:

• The room it was used in, such as the hallway or the main bedroom.
• The colour name.
• The brand and product.
• The sheen, such as matt, low sheen or semi gloss.
• The date it was used.
• The batch number, if the tin shows one.

The brand and sheen matter as much as the colour. Wattyl says touch-ups should use the exact same paint brand, colour and sheen, because even small differences in formulation can show as a mismatch. Our wall cleaning guide covers when a mark can be washed off and when it needs paint.

Lost the label? Wattyl says its Colour Match Service can recreate paint from a can with a faded label or no name.

Has the paint gone off? Stir it first, then check the smell

Old acrylic paint is usually still fine if it stirs back into a smooth, even mix. Answering whether acrylic paint goes off, Haymes says that as a general rule, if paint can be readily stirred into a uniform condition, it's still OK to use, whatever its age. Here's how to check a tin you've found at the back of the shed.

1. Stir it properly. Wattyl says to always stir paint thoroughly, because colourants can settle over time.
2. Check for lumps. Wattyl says to throw out paint with lumps that won't mix.
3. Smell it. Haymes says water-based paint can be attacked by bacteria, which causes a foul smell, though it says this happens very infrequently these days. Wattyl says to throw out paint that smells sour.

If it passes all three, brush a little on a hidden spot and let it dry before you touch up anything in plain sight. If it fails, it goes to a drop-off point, not the drain.

Getting rid of old paint: Paintback and council drop-off, free

Unwanted paint on the Sunshine Coast can be dropped off for free. Sunshine Coast Council lists paint, up to 100 litres, as a free item for domestic customers at its Beerwah, Buderim, Caloundra and Nambour resource recovery centres. Paintback, the paint industry's national scheme, also says drop-off is free for DIY and trade painters.

Paintback's rules on how to bring it:

• Up to 100 litres per visit, in containers of 20 litres or less.
• Measured by the tin, not the paint. Paintback counts the size of the container, not how much paint is left in it.
• Original tins, unmixed. Paint must be in its original packaging and not mixed with other paint.
• Empty tins are welcome. Paintback takes empty cans and pails with dried paint inside.

Paintback's location finder at paintback.com.au lists drop-off points, or call 1300 390 380. Paintback says many Australian states limit how much chemical you can carry in a vehicle, and its 100 litre cap supports those laws, so a big clear-out may need two trips.

Thinners, solvents and other household chemicals aren't Paintback items. Sunshine Coast Council takes household chemicals free in domestic quantities, up to 20 litres, at the same four centres, in their original containers. Council says they don't go in your bins at home.

Small amounts, wash water and empty tins: keep paint out of the drain

Liquid paint never goes down a drain. Dulux says never to pour unwanted paint down household or stormwater drains, and Wattyl says the same. For the scraps that don't justify a trip, the makers give these options.

• A little water-based paint. Dulux's Waste Paint Hardener turns it solid. Scoop the hardener into the tin, stir until the paint sets, leave it 2 hours with the lid off, then wrap it in newspaper and put it out as hard waste.
• A little oil-based paint. Dulux says to pour it onto kitty litter, cardboard or shredded paper, let it dry, and put it in your normal household rubbish.
• Brush and roller wash water. Wattyl's method for water-based paint: rinse in a bucket, let the solids settle, pour the clear water on the garden (not a drain), and put the dried sludge in household rubbish. Wattyl says to check council rules.
• Empty tins. Wattyl says to let cans drain and dry with the lids off in a ventilated spot, and that most councils accept empty, dry metal cans in recycling. Check your council first, or drop them at Paintback.

Paint that's still good can go to a new home. Wattyl says many community groups and theatres accept sealed, usable paint, so ask first. And paint shops can't take it back: Paintback says retail and trade outlets aren't equipped or licensed to handle liquid waste.

Buying less next time, and getting it painted

The easiest leftover to deal with is the one you never bought. Our guide to how much paint you need works out litres room by room, so you end up with enough for the job plus a touch-up tin, not a shelf of half-full ones. For what's in each kind of tin, from acrylic to enamel, see our guide to types of house paint.

Our interior house painters work across the Sunshine Coast, and the suburbs we cover are on our locations page. We've painted Sunshine Coast homes since 1985 and hold QBCC licence 1281728. Get a guide price from our instant estimate.