Polished Plaster · 01How it is built up
The wall is primed first, because lime needs something to key into and a primer stops the plaster drinking in unevenly. After that the coats go on thin. The first is a laying coat that covers and levels; the ones after it are pressed on with a flexible steel trowel and taken back to almost nothing, so each pass adds colour and depth rather than thickness. The finished build is thinner than a coat of paint feels. Then comes the burnish: the same trowel, held flat, worked over the surface at the right point of set, compressing the marble until it starts to reflect. Wax goes on last and is buffed in by hand.
Polished Plaster · 02The wall underneath decides it
This is the part people underestimate. A polished surface reflects, and a reflection shows every hollow, every patched chase and every wave that flat paint hides. Before we quote a room we survey the walls and say honestly whether they want skimming or boarding out first. On sound new plasterboard the work is usually straightforward. On an old wall carrying fifty years of repairs it may not be, and the preparation can cost more than the plaster. The finish also wants a wall that does not move. Solid masonry and sound board are fine. A flexing timber frame or loose lath is not, and there marmorino or limewash is the better answer.
Polished Plaster · 03Colour, and where depth comes from
Colour goes in at our studio, so the tub arrives already the shade you chose rather than something you stir a tint into on site. Bring us a reference and we match it. The thing to understand is that a polished wall is never one flat colour. Because the coats are translucent and laid at different pressures, you see through the top layer into the ones below, and the wall shifts as you walk past it and as the daylight turns. Deep colours show that movement most. Very pale ones read closer to a smooth painted wall with a sheen on it. Our colours page explains how to choose, and a sample board settles it faster than any screen will.
Polished Plaster · 04Wax, sheen and water
Left bare, burnished lime is already hard and already carries a sheen. Wax takes it further: it closes the surface, deepens the colour and lifts the shine, and it is what most people mean when they picture a Venetian wall. Natural bees wax is the usual choice, and a metallic wax pushes the wall somewhere else again. Wax also gives useful water resistance, which is why polished plaster sits happily on a bathroom wall, behind a basin, or in a cloakroom. It is not the answer inside a shower enclosure or a steam room, where standing water and constant heat ask for tadelakt instead. Kitchens are fine away from the hob, where grease and heat are a separate problem.
Polished Plaster · 05Living with a polished wall
It is stone, so it behaves like stone. It does not scuff the way emulsion does, it does not trap moisture behind a film, and it goes on hardening long after the trowel has left it, touch dry in hours, properly hard over weeks. Clean it with a damp cloth or a plaster cleaner made for lime. Anything abrasive or strongly acidic will dull the burnish, so keep the bathroom sprays away from it. Marks that do appear can often be worked out with wax and a cloth rather than a repair. Damage that goes deeper is patchable, though a patch on a reflective surface wants a skilled hand, and ideally the hand that laid it. Ours come back.
Where It Is The Wrong AnswerWhere polished plaster is the wrong answer
Not inside a shower enclosure or a steam room, where standing water and constant heat are tadelakt’s territory. Not directly behind a hob. Not on a wall that moves, a flexing timber frame, loose lath, or an extension still settling. And not over a wavy, badly patched wall unless you are prepared to pay to make it flat first, because a reflective surface will find every dip in it.
Yourself, Or UsLaying polished plaster yourself
Honestly, this is the hardest finish we sell. The material goes on easily enough. The difficulty is the burnish, which has a short window on any given patch, and if you miss it the wall stays dull or the trowel drags a mark across it. That, plus the flatness the surface demands, is why most first attempts read as textured paint. If you want to lay it yourself, come and learn it at the Academy. If it is your own hallway and you get one go, let us do it.
Order a sample board and put it on the actual wall, in the actual light, before you commit a whole room to it. If you would rather we laid it, ring 07592 929191 and tell us about the wall.
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