How long does leftover interior paint last?

Sealed well and stored at moderate temperatures, unopened or carefully resealed water-based paint often stays usable for years, and the label or manufacturer can give a guide. Paint that has been frozen, baked in a hot garage, or left with a poorly sealed lid spoils much sooner. Check it before you rely on it.

How do I know if old paint has gone bad?

Open it and stir it thoroughly. If it smells sour or rotten, has lumps that will not stir out, has a rubbery skin with gritty bits under it, or stays separated after mixing, it should not go on the wall. A small test patch on a hidden spot will also tell you whether it still dries to the right color and sheen.

Why does a touch-up show even with the original paint?

Usually because of sheen, texture or the surface underneath rather than color. A brush dab on a rolled wall has a different texture, an unprimed filler patch absorbs paint differently, and a wall that has been scrubbed may have a slightly shinier surface. Matching the tool and priming patches solves much of it.

Where should I store paint in a San Diego home?

Somewhere indoors with a steady, moderate temperature: a hall closet, a laundry cupboard or a shelf in a conditioned utility room. Inland garages in El Cajon and Santee can get very hot in late summer, and heat thickens and spoils paint. Keep cans off concrete floors and out of direct sun.

Touch-Up Paint: What to Keep and Store

After an interior repaint, keep a small, sealed amount of each wall, ceiling and trim paint, labeled with the room, color name and number, sheen, product line and date. Store it indoors, away from a hot garage, and stir it well before use. Touch up with the same kind of tool the wall was painted with, in a thin feathered coat, and prime any filled patch first.

The end of an interior paint job usually leaves a few partial cans behind, and most of them end up on a garage shelf with a smear of color on the lid and no other clue to what is inside. Two years later, when a doorknob dents the hallway wall or a picture comes down and leaves a hole, nobody is sure which can belongs to which room, whether it is still good, or why the patch looks different from the wall around it.

A little care at the end of the job makes those small repairs straightforward for years.

What should you keep after a repaint?

Keep a small amount of every paint used: each wall color, the ceiling white, and the trim and door enamel. A quart or so of each is plenty for touch-ups. More than that tends to sit unused and spoil. Keep the color and product information even if you do not keep the paint, so the same paint can be mixed again later.

Label it properly

The smear of paint on a lid tells you the color family and nothing else. A useful label has six things:

The room and surface, such as “main bedroom walls” or “all interior doors”.
The color name and number, exactly as the store printed it.
The manufacturer and product line, Dunn-Edwards or Sherwin-Williams and the specific line, because the same color in a different line can dry to a different sheen.
The sheen: flat, matte, eggshell, satin or semi-gloss.
The date the room was painted.
The batch or formula sticker, if the store put one on the can. Keep it, or photograph it.

A short list on paper or in your phone with the same information is worth having too, because cans get thrown away and labels fade. When Ebenezer finishes a job, this is the information to ask for.

How to store it

Paint is ruined mostly by air, heat and freezing.

Seal it well. Wipe the rim clean before closing so the lid seats fully. Laying a piece of plastic wrap over the opening before tapping the lid down helps keep air out.
Move small amounts to small containers. A third of a gallon at the bottom of a gallon can sits under a lot of air, which skins it over. A clean, airtight quart container, clearly labeled, keeps it better.
Keep it indoors. Inland garages in El Cajon and Santee can get very hot in August and September, and heat thickens and spoils water-based paint. A hall closet or a laundry cupboard with a steady temperature is better.
Off the floor, out of the sun. Concrete floors draw moisture and rust can bottoms; sun through a window heats a can more than you would expect.
Freezing is rare in most of San Diego County, but paint that has frozen and thawed can turn grainy and should be checked before use.

Checking old paint before you use it

Open the can and stir it thoroughly, all the way to the bottom, for longer than seems necessary. Pigment settles over time. Then look for warning signs: a sour or rotten smell, lumps that will not stir out, a rubbery skin with grit underneath, or paint that will not stay mixed. If the skin is clean and the paint under it is smooth, lift the skin out in one piece and strain the paint through a mesh strainer.

Before touching up a wall people will see, try a small dab on a hidden spot, such as inside a closet, and let it dry. Paint always looks darker or lighter wet than dry, so judge it only once it has dried completely.

How to make a touch-up blend

Interior touch-ups mostly go wrong for reasons other than color.

Prime the patch. Filler and spackle absorb paint differently from a painted wall. Painted over without primer, a filled nail hole often shows as a dull spot. Spot-prime the patch first, let it dry, then paint.

Match the tool. A wall that was rolled has a fine, even stipple. A dab from a brush leaves a smooth spot with ridges at the edge. Use a small roller with a similar nap for walls, and a brush for trim that was brushed.

Go thin and feather out. Load very little paint, apply it in a thin coat, and work the edges outward so there is no ridge where the touch-up stops. Two thin coats beat one thick one.

Respect the sheen. Flat and matte paints hide touch-ups far better than eggshell and satin. On a shinier wall, a touch-up is more likely to show at an angle, and repainting the wall from corner to corner may be the cleaner answer.

When touch-up is not the answer

If the wall has faded in sunlight, been scrubbed hard, or is several years old, even the original paint from the original can may no longer match the wall, because light and cleaning have moved the wall away from what is in the can. Rooms facing west in Chula Vista and East County see a lot of afternoon light, and color shifts over time there. In that case, painting the whole wall to its corners hides the repair; patching one spot does not.

Small repairs are welcome work. If a wall has a few dings, a patch that keeps showing or a room that needs refreshing, Ebenezer will look at what you have and tell you honestly whether a touch-up will blend or whether the wall needs painting. Every client gets the same care, and no job is too small. More on interior painting, or ask for a free estimate.