Tesera sets every mosaic portrait in lime mortar on a 12 mm birch panel that is sealed before anything touches it. Lime mortar is the bed the basilicas were set in, and it holds glass and ceramic without the panel moving; the sealed birch will not warp. Together they are why a panel hangs flat and stays that way.
What does lime mortar do in a mosaic?
It is the bed. Each tessera is pressed into wet lime mortar and held there as it sets, so the piece is fixed by the mortar around its sides and under its base, not stuck down by a glue on its back.
A tessera cut with a hammer does not have a flat back. The mortar takes up the difference under each piece, so the surface can be levelled by hand as it is set and every face ends up where the maker wants it. That is the quality you see from across a room: the pieces sit at their own angles, but the panel as a whole is even.
Lime mortar cures slowly, and slower still in damp weather. One spring a panel waited an extra week for its mortar to cure before we would crate it; worth it, and we told the buyer so, though later than we should have. How long a portrait takes covers what that means for a date.
Why a birch panel, and why 12 mm?
Because a mosaic needs a base that will not move. The panel is 12 mm birch, sealed before the mortar goes on, so the damp of the mortar cannot get into the wood and bow it.
| Part | Specification | Why |
|---|---|---|
| Panel | 30 × 30 or 50 × 50 cm | Two square sizes, the same build in each |
| Substrate | 12 mm birch, sealed | Stiff enough to carry the glass, sealed so it will not warp |
| Bed | Lime mortar | Holds each tessera around its sides as it sets |
| Tesserae | Glass smalti and glazed ceramic, 8–14 mm | Cut by hand with a hammer and hardie |
| Hanger | Keyhole, fixings included | One screw through the back, and the panel sits flat |
| Back | Signed | Every panel leaves the studio signed |
The keyhole hanger is on the back of that same panel, which is why a single screw is enough to hang either size. The hanging guide walks through it.
What happens after the mortar sets?
Once the mortar has set, the joins are grouted, the surface is cleaned and then waxed. Grout fills the gaps between the pieces; wax is the finish you see and touch.
- The grout goes over the whole surface and into every join, then the excess comes off
- The surface is cleaned until each face of glass and glaze reads clear
- The panel is waxed, which seals the surface and brings the colour up
- The finished panel is checked against the approved design
- The back is signed, and the panel goes into its crate
Does the panel need any care because of the mortar?
Very little. Dust it with a dry cloth, and never soak the grout. Direct sun is fine, because it is glass and clay.
The mortar and the grout are the one part of the panel water can get into, which is why the care instruction is a single line. The glass and the glaze do not care about light or heat. The care guide has the longer version.
Why does this matter when you buy?
Because the bed and the panel are what a photograph cannot show you. Two mosaics can look alike on a screen; whether one still hangs flat years from now depends on what is behind the glass.
Every panel we set is built this way, whether it is a shop piece or one drawn from your photo. If you want to start one, upload a photo and Tedooo draws it in about a minute; the lime mortar and the birch are what we set it in after you approve.
Questions this leaves
How long does the mortar take to cure?
Long enough that it happens inside the two weeks a panel takes to make, and longer in damp weather. We do not quote a figure, because it moves with the season. If a panel needs an extra week for its mortar before we will crate it, we hold it and we tell you.
Can the panel warp?
The birch is sealed before the mortar goes on, so the damp of the setting cannot get into the wood. That is the point of sealing it: a panel that stays flat on the wall. Keep the grout dry once it is hung and nothing about the panel should move.
Is the back finished?
The back carries the keyhole hanger and our signature. Every panel leaves our US studio signed, which is how you know who set it. The fixings for the keyhole are included in the crate, so there is nothing else to buy before it goes up.
