Venetian Plaster Samples, Testing Colour with Sample Boards

Test a Venetian plaster colour on a sample board, laid in the finish you have actually specified, and look at it in the room it is going in, upright, in daylight, next to the floor and the fabrics it has to live with. A paint chip cannot tell you what a lime plaster will do, because half of what you are judging is not colour at all: it is sheen, depth, trowel movement and the way light moves across a burnished surface. This is how we test colour with sample boards, and the mistakes that cost people a whole wall.

Testing colour properly takes a few days and costs very little. Getting it wrong costs a recoat, so it is the cheapest part of any job.

Why a colour chip is not enough for Venetian plaster

A printed chip or a paint card is flat, matt, small and lit by whatever is above your head in a shop. A finished plaster wall is none of those things.

Three things change between the chip and the wall. First, sheen. The same pigment burnished to a high polish reads darker and richer than the same pigment left matt, because a polished surface reflects the room back at you. Second, depth. Venetian plaster is built in coats, and light enters the surface and bounces around inside it, so the colour has movement in it rather than one flat value. Third, lime. Lime based finishes dry lighter than they look wet, sometimes considerably, and they keep lightening as they carbonate. Judging a lime colour while it is still damp is the single most common error we see.

None of that is a reason to distrust the material. It is a reason to test it in the form it will take.

What a sample board should be

A proper board is the specified colour, in the specified finish, at the specified sheen, applied the way the wall will be applied. If the wall is polished plaster burnished to a high gloss, a matt Marmorino board tells you very little. If the finish is Marmorino with a soft trowel texture, the board wants that same movement in it.

Size matters more than people expect. A small square surrounded by white primer will read darker than the finished wall, and it will not show you the tonal drift a trowelled finish has across a larger area. Bigger is always better. Two boards of the same colour placed side by side give you a better read than one, because you can see how the finish looks where two passes meet.

We sell boards ready for this: a single sample board at £8, the sample box of six boards at £35, and the sample case at £150 for designers and showrooms who need a full set to present from. Colours themselves start on the colours page.

How to judge a board once you have it

Take the board to the room, not the room to the board.

Hold it upright. A board flat on a table is being lit from above, which no wall ever is. Tape it to the wall it represents, in the place it represents.

Look at it three times a day. Morning light, afternoon light and artificial light at night. A north facing room will pull a warm grey towards blue; a south facing room in the afternoon will pull the same grey towards brown. If the room has a lamp lit evening life, that matters as much as the daylight.

Check it against what it has to sit next to. Bring the flooring sample, the worktop offcut, the curtain fabric and the paint you intend to use on the woodwork. Colour is only ever relative. A plaster that looks perfect against bare plasterboard can go sour against a warm oak floor.

Rake the light across it. Stand so a window or a lamp throws light along the surface rather than straight at it. This is how you see trowel movement and sheen, and it is how a wall will look from the doorway. Metallic finishes must be judged this way, a liquid metal or a metallic polished plaster changes completely between direct and glancing light.

Wait until it is dry. With lime, give it days rather than hours before you sign anything off.

Testing colour for a scheme, not just a wall

If you are specifying for a client, the board is a document as well as a test. We tint to your colour in the tub, and the reference is recorded, which is what makes a second batch months later match the first. That matters on phased projects, on snagging, and on any repair down the line.

A few habits that save trouble:

• Write the colour reference, the finish, the sheen and the date on the back of every board, and keep one. The board you keep is the one you compare a repair against in three years.
• Approve the sheen separately from the colour. They are two decisions and clients conflate them constantly.
• Where a scheme runs across several finishes, test them together. A limewash ceiling above a polished plaster wall has to be tested as a pair, not as two nice boards in different rooms.
• On large or high value walls, a sample board is the start and a sample area on the actual wall is the finish. Nothing tells you more than the real substrate in the real light.

Matt lime finishes need their own care here, because limewash dries dramatically lighter than it goes on and its whole character is cloudy variation. Our guide to choosing limewash colours goes into that, and choosing colour for Venetian plaster covers the broader question of picking a colour that will still be right in five years.

Questions we get asked

Can I get a sample of Venetian plaster before ordering?

Yes. We sell prepared sample boards individually at £8, as a box of six at £35, and as a full sample case at £150. Boards are the right way to test, because they show you the finish and the sheen as well as the colour. Order them from the shop and tell us the colour reference and the finish you are considering.

Why does the plaster look different on the wall than on the sample?

Usually scale, light or sheen. A small sample surrounded by a different colour reads darker, a wall reads lighter across a large area, and the direction of the light in the actual room changes the surface completely. If the finish or the burnish differs from the board, the colour will differ too, which is why we match both when we make a board.

Does Venetian plaster dry lighter or darker?

Lime based finishes dry lighter than they appear wet, and they carry on lightening as they cure over the following weeks. Acrylic based finishes move less. This is why we never let anyone approve a lime colour from a damp board, and why a test needs days rather than an afternoon before a decision is made.

How many colours should I test?

Two or three, chosen deliberately. More than that and you stop comparing and start guessing, because the eye loses its reference quickly. Pick one you think is right, one slightly lighter and one with a different undertone, then live with all three on the wall for a few days and let the room decide.

Where to go next: browse the range on the colours page, then order boards from the shop with the finish and reference you want them made in. If you would rather we prepared a sample area on the actual wall before committing, that is something our applicators do as part of a quote. Call 07592 929191.