There are four methods of making a mosaic, and the right one depends on the surface, not on skill alone. Direct means setting tesserae straight onto the final surface. Indirect means building the mosaic face-down on temporary backing and transferring it. Double direct builds it on fibreglass mesh. Double indirect builds it on adhesive-backed paper, face visible, and is the hardest of the four.

This guide covers the methods and when each applies. If you want the practical starting point — tools, adhesives, cutting shapes, grouting — that is in our guide to how to start mosaic art.

The four methods compared

The direct method

You glue each piece, face up, onto the surface the mosaic will live on. That is all there is to it — which is why it is where everyone starts.

Its real advantage is that you see the mosaic develop as you work. Nothing is hidden, nothing is reversed, and a mistake is visible immediately. It also tolerates mixed materials freely, so found objects, broken china, pebbles and shells can go in alongside cut tesserae without any planning for thickness.

It is the only sensible method for anything three-dimensional. A birdbath, a planter, a vase — there is no way to build those face-down on a flat board.

The limitation is flatness. Setting pieces individually by hand means slight variation in height, which on a tabletop or floor is both visible and unpleasant underfoot.

The indirect method

Also called the reverse method, and the name explains it: the mosaic is assembled face-down on a temporary backing, held with water-soluble glue. When it is complete the whole sheet is transferred onto the final surface, and the backing is wetted and peeled away.

Two things make it worth the trouble. Because every piece is pressed against a flat board while the adhesive cures, the finished surface is genuinely flat. And because the work happens at a bench rather than in situ, the precision is better.

This is the method for tabletops, floors and murals — anywhere flatness matters and the surface is large. It is also how large commissions are made in sections and assembled on site.

The difficulty is obvious: you are working on the back of the image. Everything is mirrored, and you cannot see the face you are composing until it is finished and flipped.

The double direct method

The compromise, and a genuinely useful one. Tesserae are set face-up onto fibreglass mesh, which is then bedded into adhesive on the final surface.

You keep the direct method's advantage of seeing the work as you go, but gain portability — the mosaic can be moved around during construction, carried to the site, and positioned as a sheet rather than piece by piece.

It is the best answer for curves. Mesh flexes, so a design can be wrapped around a pot, a vase or a rounded wall in a way that neither direct nor indirect handles well.

This is also how most commercially supplied mosaic arrives — pre-assembled on mesh in sections, which is why installing a bought mosaic is much easier than people expect.

The double indirect method

The hardest of the four, and genuinely for experienced makers only.

Tesserae are layered onto adhesive-backed paper in a way that keeps the faces visible during assembly, then the whole thing is transferred. It solves the indirect method's central problem — working blind on the reverse — while keeping the flat, precise result.

The cost is complexity. There is an extra transfer stage, and every transfer is an opportunity for pieces to shift. It is used where a design is intricate enough that the maker cannot afford to work mirrored, but the finish still has to be perfectly flat.

Planning a large project

Scale changes the problem. Past a certain size a mosaic stops being something you make and becomes something you have to plan, and two habits make the difference.

The first is a sketched layout done properly before any tesserae are cut — not a rough idea but a full-size plan showing where the main lines fall, because on a large piece an error compounds across the whole surface rather than staying local.

The second is sectioning. Large mosaics are built in parts on separate backings and assembled on site. It makes the work transportable, lets more than one person work at once, and means a section that goes wrong can be redone without touching the rest. The indirect method suits this particularly well, since each section is already being made on its own temporary backing.

The joins between sections need planning too — run them along a natural line in the design rather than straight through the middle of a face, and they disappear.

Micro mosaic

At the far end of the craft is micro mosaic, which the Romans called opus vermiculatum — from vermiculi, "little worms", after the winding lines the tiny pieces form.

The numbers are what make it remarkable. Tesserae measure one to two millimetres. A single centimetre-long tile yields five rows of them, which is what allows the colour variation to be so fine. An abstract micro mosaic in 1 mm tesserae takes one to two weeks to complete, because each piece has to be placed so that the colours resolve without a picture to guide the eye.

Size is limited by the nature of the work — usually 20 to 40 centimetres at most. The Romans made them in a workshop on an independent support and then set them into a floor, which meant a micro mosaic could be lifted out and moved to another building. Portable art, in stone.

The glass rods used for the smallest pieces are drawn by a spinning technique to get them thin enough.

Micro mosaic reproductions

Micro mosaic is the technique used to reproduce paintings, and there is one material rule that decides the result: marble rather than glass.

Glass reflects. On a painting reproduction that reflection fights the image, so artisans use marble tesserae instead — matte, stable, and colour-fast over time. This approach was developed after the completion of St Peter's Basilica, where the workshops had both the skill and the motivation to render paintings permanently.

The same method is used today for Van Gogh's Sunflowers, for Picasso, and for Magritte — works whose flat colour fields suit tesserae better than anything with delicate brushwork.

Micro mosaic as ornament

In the twentieth century micro mosaic moved off the wall and onto objects. Watch faces, jewellery, furniture inlay — pieces small enough that 1 mm tesserae are the only way to get an image onto them at all.

The design language came largely from Gustav Klimt and Antoni Gaudí, whose work translates unusually well into small tesserae, alongside the traditional subjects: Roman monuments and religious iconography.

Making a mosaic: the practical sequence

Whichever method you use, the sequence is the same.

1. Start simple. A cartoon-like image or basic geometric shapes, before anything complex.
2. Sketch the design at full size on a sturdy base — plywood or concrete board — using simple dotted outlines as placement guides rather than a detailed drawing.
3. Cut the tesserae. For glass, use a wheeled glass cutter, and wear safety goggles without exception.
4. Lay the pieces, keeping the gaps no larger than one eighth of an inch. Wider than that and the piece reads as scattered rather than assembled.
5. Let it dry completely before grouting.
6. Grout, then clean.

Cheap practice material is worth using while you learn: cast-off ceramic tiles and natural pebbles cost nothing and teach the same lessons as expensive tesserae.

Choosing grout colour

Grout colour changes a mosaic more than most people expect, because the grout lines are a significant proportion of the surface.

The general rule is contrast: black grout under white tiles makes every piece read as a distinct unit and the pattern becomes legible from across a room. Matching grout does the opposite, dissolving the pieces into a single field.

One thing to plan for: grout colours fade as they cure. What you mix is darker than what you end up with, so choose on the expectation that it will lighten.

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