Identifying the Existing Sheen and Coating Before a Repaint
Why this matters
Most repaints start with nobody knowing what is on the wall. The previous painter is gone, the leftover can went out with the last move, and the customer remembers the color name but not the sheen or the maker. Guess the sheen and a one-wall repaint or a patch flashes, a dull or shiny patch you can see from the doorway. Guess the chemistry and new latex over old oil peels off at a fingernail. Both are found out after the crew has left, and both are fixed at the shop's cost. This card covers reading the existing sheen against samples and reading the existing coating with a few quick tests, before the bid and before the first can is opened.
Two questions, answered separately
Every existing surface asks two things, and one answer does not tell you the other:
- What sheen is it? That decides what the new coat must match where it meets old paint, and it is a visual match.
- What is it made of? That decides whether the new coat will stick. 'Latex' here means waterborne acrylic and 'oil' means solvent alkyd. A satin latex and a satin oil look alike at arm's length and need different prep.
Answer the chemistry first on trim, doors and anything that was ever enamel, because a wrong answer there ruins the job no matter how well the sheen matches. Answer the sheen first on walls and ceilings, where the coating is almost always latex in any house painted in the last few decades, though an old house can still carry oil on a kitchen or bath wall.
Why a sheen name is not a sheen
Sheen names are not standardized between makers. One maker's eggshell can sit closer to another's satin, and the same name can step up or down within one maker's product lines. 'Paint Sheen + Finish Guide' covers what each sheen does; this card's point is narrower: the match is made against a physical sample, never against a name. "It's eggshell" from the customer, or even from the old can, tells you which samples to bring, not which one to buy.
Gloss is measured with a gloss meter under ASTM D523, at a 60 degree angle for most finishes, 20 degrees for high gloss, and 85 degrees for flats, where the near-grazing reading separates low-sheen finishes the 60 degree reading cannot. A meter is useful for a shop that does a lot of matching. The method below works without one.
Reading the sheen against samples
- Find an untouched reference spot. The field of a wall away from switches, door edges and furniture, in an area the light will reach. Sheen changes with wear: flat and matte finishes burnish up where hands and chairs rub, so the area beside a light switch reads glossier than the wall it sits on. Outside, sun and chalking dull a gloss finish over the years. Match to what the new coat will sit next to, which is usually the field of the wall.
- Clean the spot. A damp cloth and mild cleaner, rinsed and dried. Kitchen grease and dust change apparent sheen in both directions.
- Bring the line's samples as brush-outs, not chips. Paint the candidate sheens of the line you will use onto primed cards, at least two coats, and let them dry fully per the data sheet. Sheen keeps changing as a coat dries and can take days to settle; a sample read wet or half-dry misleads.
- Hold the sample flat on the wall and look at a low angle to the light. Stand so the light (a window, or a work light held to one side) skims the wall and reflects toward your eye. At that angle the difference between two sheens shows as a difference in glare. Viewed straight on, two sheens a full step apart can look the same.
- Bracket it. Hold the two nearest samples side by side against the reference spot. The right one disappears into the wall; the one either side of it reads as a patch that is shinier or duller. If the wall falls between two of the line's sheens, the match is not available in that line, and the choice becomes a different line or a corner-to-corner repaint rather than a patch.
- Read it in the customer's light, at the time of day they see the room. A match under a morning work light can fail under late-afternoon sun raking across the wall.
The old touch-ups tell you something
Before you match anything, walk the room looking for previous touch-ups at the same low angle: spots and rectangles that read as a different sheen from the wall around them. They tell you three things:
- The wall has been patched before, often with a different sheen or a different product, so the wall itself may not be one sheen everywhere. Match to the largest uniform area, and expect that a full wall repaint will be easier to sell than a patch.
- Where the previous painter's patch flashed, the wall is sensitive to touch-ups. A flat that flashes under a patch of the same product is telling you application matters as much as sheen; see 'How to Touch Up Paint So the Patch Does Not Flash'.
- Where touch-ups vanished, the wall's sheen and the product used to touch it up agreed. If the customer has that can in the garage, it is the most valuable thing in the house.
Reading the coating itself
| Test | How | What it tells you |
|---|---|---|
| Alcohol rub | Denatured alcohol on a cotton ball, about twenty strokes on a cleaned spot | Color comes off and the spot softens: latex. Clean cotton, surface unchanged: treat as oil. |
| Fingertip wipe | Drag a dark fingertip or cloth across exterior paint | White or colored powder: the surface is chalking, and it must be washed off before any test or coat. |
| Fingernail | Press and drag at an edge or old chip | Lifts in sheets from a glossy layer below: the top coat is already failing over something it never bonded to. |
| Look at chips | Edge of any existing chip or failure | Count the layers and look for a hard, glossy, often cream or yellow layer: old oil enamel. |
| Thickness and stretch | Exterior masonry, stucco | A thick, rubbery film that stretches before it breaks: elastomeric, which most conventional paints will not bond to well without the maker's guidance. |
The alcohol test reads only the top coat, and it can misread a few waterborne alkyds and urethane-modified enamels as oil, which is the safe direction. Alcohol also dissolves shellac and softens some lacquers, so a stained or clear-finished surface that turns gummy is not latex. The test procedure, its limits and the adhesion check that goes with it belong to 'How to Test Glossy Trim and Prime Latex Over Oil'.
Lead. In any pre-1978 house, presume lead until an EPA-recognized test kit or a certified renovator's sample says otherwise. A cotton-ball alcohol test and a gentle look at an existing chip disturb a trivial area. Scraping into the layers to count them is disturbance, and it waits for the test.
Worked example: one wall in a living room
The request. The customer had a contractor open and patch a 3 foot by 2 foot section of drywall on a living room wall after a plumbing repair. The walls were painted about six years ago; the color name is known, the sheen and maker are not, and no paint was left behind. The customer wants the patch to disappear.
First read. In the field of the wall, at a low angle to the big window, the finish showed a soft glare: not flat, not as shiny as satin. Beside the light switch it read noticeably glossier, which is burnishing, so the switch area was not used as the reference.
Old touch-ups. Two small rectangles low on the wall read duller than the field. The previous painter had touched up nicks with a flatter product, and they had flashed. So the wall was not perfectly uniform even before the plumber arrived.
Chemistry. On walls of that age the coat was assumed latex, and an alcohol rub behind the sofa confirmed it: color on the cotton, spot softened.
Samples. The lead brushed out the line's matte, eggshell and satin, color-matched, on primed cards, and left them overnight. Against the reference spot at the window angle the next morning: matte read clearly duller, satin clearly shinier, eggshell nearly disappeared but read slightly brighter when the afternoon sun came round.
The call. A patch in the middle of the wall with a sheen a hair off would flash in the afternoon. The wall runs corner to corner without a break, so the lead recommended painting the whole wall in the eggshell, corner to corner, and leaving the other walls. A slight sheen difference at an inside corner is hidden by the change in light on each plane. The customer agreed after seeing the eggshell card held on the wall in the afternoon.
What would change the answer.
- The customer had the old can. A patch would be worth trying, primed first so the new drywall mud does not drink the topcoat, then touched up with the original product.
- The wall was flat. Flats hide small sheen differences far better than eggshell, and a patch in the field would have stood a better chance.
- The wall was in a kitchen with old paint of unknown age. The alcohol test comes first, because an oil wall changes the job from a sheen problem into an adhesion problem.
How to know you read it right
- The brush-out disappears against the reference spot at a low angle in the light the customer uses, after it has fully dried.
- The test results are written on the bid for each surface type: walls, trim, doors, exterior body.
- Any surface where no sample matched is bid as a corner-to-corner or edge-to-edge repaint, not as a patch, and the customer knows why before work starts.
References
- ASTM D523, Standard Test Method for Specular Gloss (current edition)
- See related: Paint Sheen + Finish Guide
- See related: How to Test Glossy Trim and Prime Latex Over Oil
- See related: How to Touch Up Paint So the Patch Does Not Flash
- See related: Lead Paint RRP Protocol Reference