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What Is Thinset Mortar?

For outdoor and wet mosaics, thinset is recommended instead of adhesives. Thinset is a bonding mortar, which means it is a portland cement (the same as used in concrete) with polymers added to make it sticky and extra strong. This is particularly important when working with glass mosaic tile, which is non-porous and difficult to bond securely.

What Brand?

We now sell thinset mortar in 2.25-pound convenience packs for small projects.

We use Versabond brand, which we buy at Home Depot, and I suspect your local contractors are using the same or something more or less the same. HOWEVER, if you live some place with extreme cold or extreme wet, it never hurts to go to your local building material store and ask what contractors are using in your area before choosing a paint or a roofing material or a sealant or anything like that.

How To Handle Large Bags?

Thinset Mortar comes in 25-pound bags. Go ahead and buy a 5-gallon bucket with a snap on lid and keep your material in there. Bags leak. Buckets with lids don’t. Slide the bag into the bucket and shake it until the bag fits into the bucket. Avoid pouring the bag into the bucket, which would make a large dust cloud. Keep a recycled plastic yogurt tub in the bucket and use that to scoop out material. Wear a dust mask and do this outside. Mist with a spray bottle to control dust.

Mixing Thinset Mortar

The thinset bag has mixing instructions on the label, but those were written for mixing the entire bag. For detailed mosaic artwork where you are placing each tile by hand, you will probably want to mix 1 to 3 pounds at most. You can find what amount of water to add per pound by dividing the amount of water recommended for the entire package by the weight of the package.

Mixing Ratio: 4 oz Water to 1 lb Thinset

For Versabond thinset, we add 1/2 cup or 4 oz of water per 1 pound of dry thinset powder. You can use that same ratio of 1 part water to 4 parts thinset to mix up tiny batches of thinset, such as 1 ounce of water plus 4 ounces of thinset.

Mix Outdoors and Control Dust

We use a small kitchen scale or postal scale for weighing out the thinset and the water. Alternatively, a measuring cup can be used for the water, with 1/2 cup being the equivalent of 4 ounces weight. Although you should wear a dust mask when scooping and mixing the thinset powder, it is best to control dust at the source by slow careful scoops and stirs and never pouring or dumping the powder.

Use a spray bottle at its finest setting to mist your work area with water as you stir and scoop. There is only a tiny amount of water in a fine mist, and so you don’t have to worry about it messing up your unused thinset or throwing off your measurements, but it is highly effective at getting the dust out of the air. Keep in mind that you can create a lot of dust after the water is added to the powder by stirring to rapidly. Stir slowly until the powder is wetted, and make use of your spray bottle as needed.

An aluminum ice scoop or a large steel kitchen spoon can be used to scoop out the thinset powder, but you can also use a recycled plastic container (such as used for cottage cheese or yogurt) and just store this improvised scoop in your bucket of thinset.

Here is a list of items recommended for mixing thinset:

• plastic bucket or plastic container for mixing.
• smaller plastic containers for scooping and weighing
• dust mask
• small kitchen scale or postal scale
• measuring cup (optional)
• paint paddle or sturdy rod for stirring
• trowel for scraping buckets and stirring tools
• spray bottle for misting

Mixing Buckets: Size Matters

For small batches of 1 pound or less, we mix it up in a 32-ounce plastic yogurt container and use a putty knife or old butter knife to stir. For larger batches, we mix in a 5-gallon bucket so that we can mix vigorously without slinging out any material. A smaller bucket (2 gallon) can also be used, but keep in mind that you don’t want to fill any container more than half way full, ideally a quarter full or less. It helps to control dust if all the mixing happens near the bottom of the bucket.

Stirring

You have to pour the water in gently and stir slowly at first to avoid creating dust before the powder is wetted. Use a clean paint paddle or sturdy rod to stir, and make sure that your stirrer is stout enough for the job. This is concrete not cookie dough! You can break the plastic handle off your wife’s favorite spoon or bend a thin piece of pipe in a hurry if the batch is large enough. In all seriousness, you will notice that it takes some strength to mix up larger batches. We have a concrete mixing attachment that fits into our electric drill, and we use it for batches of 5 pounds or more.

Mix the mortar until it has the consistency of dough with no lumps. Take care to mix all the way to the bottom of the bucket and scrape the edges to make sure that no powder, lumps or clumps remain. Then the mortar is allowed to sit for 5 to 10 minutes, and then it is mixed again for a minute or two.

A margin trowel is very useful for scraping the sides of the bucket and making sure there aren’t pockets of unmixed powder down in the edges of the bottom of the bucket. The scraping power of the trowel comes in handy during clean up too. Thinset is very sticky, and if it has set for more than a few minutes, it will likely take more than a squirt nozzle to remove it. Scraping with a trowel is the best way to remove the crust of thinset that forms on buckets and stirrers.

Dyeing Thinset?

After the thinset is mixed, concrete dye can be blended into it if the thinset will be used for grouting and a custom color is desired. (Versabond thinset is sold in white and gray.) Most thinset is used only for attaching tiles, and so there is no need to dye the thinset if it will not be visible. Also, you need to test your dye with your thinset to make sure that it doesn’t affect the bond strength or hardness. (A good test is to cement a few rocks together, wait about 6 days, and then bust them apart with a hammer and look for crumbly material or a lack of adhesion.) Recently we added a liquid concrete dye to Versabond thinset, and we used many, many times the recommended dosage for concrete without any noticeable loss in bond strength or hardness as far as we could tell, although we make no guarantees. Keep in mind that we used a concrete dye and not acylic paint or some other source of pigment that might interfere with the adhesive additive.

Detailed Mosaic Artwork

Thinset is extremely sticky and meant to be spread with a trowel to mount large tiles or sheets of tile, but with a little care and planning, you can use it mount tile one piece at a time for detailed mosaic artwork similar to how glue is normally used in that mode of working.

As with glue, thinset can be used in either of two ways: It can be spread on a small area on which tiles are then placed, or it can be applied to the back of each tile individually. For either technique, a painter’s palette knife is the ideal tool for handling the thinset. (Although improvised tools such as an old butter knife can be used for this work, the benefits of the palette knife become obvious in just a few minutes. The pallet knife was ergonomically designed to manipulate pastes on flat surfaces WITH MINIMAL BENDING OF THE WRIST and makes a butter knife just seem clumsy.)

Whether your spread the thinset or apply it to each individual tile, you will need a way of keeping your hands clean and a way of cleaning up random drops and smears. We use the following materials to keep the work clean and efficient:

• painter’s pallet knives
• putty knife or margin trowel
• small plastic lid or tray
• tweezers
• spray bottle
• dirty rag
• wet rag floating in a bucket 1/4 full of water
• clean rag
• medical examination gloves (recommended)
• old work surface or shop table.
• wadded newspapers in garbage can

The plastic tray or recycled container lid holds a small amount of thinset for use. Scoop a small amount of thinset into the tray and keep the rest of the thinset in the mixing bucket. Keep the bucket covered and use the putty knife or margin trowel to scrap the sides of the bucket so that all the thinset is in a blob and doesn’t dry out. Mist the thinset sparingly if you see it drying. We can use thinset for up to 4 or 5 hours this way.

Whether you spread the thinset in small patches or put a smear of thinset on the backside of each tile will depend on your style and pace of work. If you are improvising your design as you go along, you may find that you use both techniques.

Keeping Fingers Clean

No matter how you handle the thinset, you will occasionally get some on your fingers. If you are sloppy in how you clean your fingers (gloved or ungloved), you will use up tons of rags. Use this procedure to use only 3 rags:

1. Scrape fingers off on the wadded newspaper in the garbage can.
2. Use the DIRTY rag if needed, but try to use as little as possible.
3. Dip fingers in bucket of water with WET rag.
4. Use the CLEAN rag to dry fingers.

If the above instructions aren’t detailed enough, I have also written an expanded version of this technique in a blog article called How To Keep Your Hands Clean When Using Thinset Mortar.

Examination Gloves Recommended

Thinset, grout, concrete, and other products that contain portland cement are mildly caustic and can dry out the skin very rapidly and cause irritation. For this reason, we wear medical examination gloves while we work with thinset. The nitril gloves we sell are ideal for this purpose because they are latex-free and powder free and are more durable than the latex medical examination gloves we used to sell. Note that these gloves are much thinner and offer much more dexterity than the thick grouting gloves.

Grouting Bag Fitted With Icing Nipple

For found-object mosaic, we sometimes use a grouting bag fitted with a Wilton brand cake icing nipple. The grouting bag with nipple allows us to dispense the thinset in a very controlled way as if from a bottle of glue. This technique can also be used for flat tile.

Clean Up

Make sure you clean up outside and do not pour unused thinset down drains. Even the sand in grout and thinset is enough to stop up some plumbing systems. Try to dispose of most of your unused thinset as solid waste. Rinse away any residue with enough water so that you don’t leave a white limestone scum on the grass, which could kill it if conditions are dry.

Millefiori is an Italian word meaning “thousand flowers.” Italian Millefiori resembles tiny pieces of Christmas candy and is made in a similar way. The process used to create millefiori has not varied much since 1400 B.C.E. when it was first made by the Egyptians.

To make millefiori, glass artists take many thin glass rods or canes and arrange them in a bundle so that they form a pattern in the cross section. The pattern can only be seen at both ends of the bundle. Once the pattern is set, the rods in the bundle are fused together into one rod with a torch. This rod is stretched thin while it is hot, allowed to cool, and then cut into slices that we know as millefiori. Sometimes millefiori is also referred to as murrine, which involves small pieces of cut glass melted together to create a larger piece of glass.

Millefiori is often used to represent flowers in mosaic art. While flowers are the most common pattern in millefiori, other designs are also popular: stars, bulls eyes, hearts, swirls, etc. The millefiori assortment we sell includes many patterns and colors. It’s great as an accent in mosaic artwork, particularly mixed-media mosaics made with various types of materials, but the pieces are rather small (less than 1/2 inch in diameter.)

The thickness is roughly around 1/8 inch, so millefiori can be used with vitreous glass mosaic tile and stained glass.

Reinforced concrete sculptures can be made from materials readily available from your local building material store, and these make great long-lasting bases for mosaic sculpture. In fact, if you thoroughly seal the finished mosaic with an outdoor concrete sealer, then the mosaic could last as long as anything made by the ancient Greeks or Romans.

Another great thing about using reinforced concrete as the base for your mosaic sculpture is that there are many techniques and materials that you can use, and you can even make hollow shapes like spheres.

The first step in making a sculpture is to build a load-bearing frame, usually out of welded rebar or angle iron (or whatever scrap steel is available), but people without access to a welder can simply drill holes in the angle iron and bolt their frame together. Expanded metal is also useful for flat shapes.

The next step is to cover the frame with wire mesh, usually either chicken wire or hardware cloth, both of which are available at most any building material store. The chicken wire or hardware cloth is “tied” to the frame with bare wire. We usually use fencing wire ties, which are sold for wiring fencing to fence posts, or concrete wire ties, which are sold for holding rebar in place. You can use whatever bare steel wire you have on hand, but I would avoid aluminum or copper because these metals will corrode steel over time. Usually 1 or 2 layers of hardware cloth are sufficient to form a surface upon which concrete can be spread, but 3 or more layers of chicken wire may be needed before your surface is firm enough. It really all depends on whether or not you are making a hollow sculpture or one that will be filled with concrete.

For hollow sculptures, expanding foam (from the building material store) can be squirted in to fill the void inside your wire frame shape. The advantage of using expanding foam is that once the foam hardens, you will have something inside the wire-mesh skin of your sculpture when you start spreading concrete on it so that the wet concrete doesn’t just fall through. Another reason to use the foam is that it will prevent moist air and water from rusting your steel frame from the inside over time. One thing you have to watch out for with expanding foam is the potential to use too much and have it expand into the wire mesh skin. Keep in mind that the wire mesh skin needs to be encased in concrete and not be merely underneath a layer of concrete. If the concrete is just sitting on top of the wire-mesh skin and not integrate with it, then it will probably break off over time like a piece of eggshell. On way to prevent the foam from expanding into the wire-mesh skin is to squirt the foam inside a trash bag inside the frame. The foam will expand inside the bag, and bag will keep it from extruding through the wire-mesh skin.

Concrete is traditionally spread with trowels, and trowels are useful for scooping up concrete and pressing it onto the surface of your mosaic, but you will probably find that working it into the wire by hand works best. The wire tends to puncture even the heaviest of rubber gloves, so we use a cheap pair of work gloves.

Ordinary concrete isn’t the best choice for sculptures because ordinary concrete isn’t sticky enough, and it isn’t strong enough in terms of tensile strength (in spite of having great compressive strength). The authors of most mosaic books explain how to add latex additives to portland cement to make a sticky concrete, but why would you do that when you could just go buy a bag of thinset mortar? I suspect these authors are just trying to posture as artists and demonstrate their technical competence, but I think they forget how many people they discourage by making things harder than they need to be. We use thinset mortar mixed with pea gravel in a 2:1 ratio (thinset:pea gravel). We sieve the pea gravel to remove all the bigger pieces that won’t fit into the wire-mesh skin.

There are a lot of different techniques used by various artists, including coating rags with thinset and layering these rags onto the frame like paper mache. You can find additional instructions and ideas online.

In recent years people have begun using hollow fiberglass shapes as bases for outdoor mosaic sculptures. Fiberglass bases might have the advantage of being lighter than traditional concrete bases, but fiberglass bases can’t as easily be made using local materials and fiberglass work requires noxious chemicals. That is why when you see a mosaic sculpture made on fiberglass base, the base was almost always pre-made in a factory in a mold, which isn’t of much use to an artist wanting to create his or her own vision. Also, hollow fiberglass mosaic shapes can flex slightly while mosaic tile and grout cannot, so the durability of mosaic sculptures made on fiberglass bases is questionable, at least in my opinion.

This page includes examples of figurative mosaic art that are particularly exuberant and joyful. I consider these mosaics to be fun and whimsical without being cute in a tired sort of way. This is no small accomplishment in my opinion. The art on this page was made using 3/8″ Glass Mosaic Tiles.

Whimsical but Fresh

I’m not a big fan of “cutesy” in art, and I really dislike how cutesy tends to dominate amateur art in general, but it is possible to be whimsical without being cliche or saccharine sweet. To understand what I mean, consider the work of famous painter Marc Chagall. Most of his paintings are playful in tone, but they are all genuine art in that they are original or take risks or are fresh in some way.

My goal for this page is to showcase work that is whimsical in tone but fresh. I’m hoping people email me pictures of their art, but I’m also hoping that their art isn’t a copy of something they saw at an arts and crafts show or on a holiday greeting card or something like that. All artists copy in one way or another, but to duplicate a craft product that is already being manufactured is a sad loss of an opportunity to make something different. Make something your grandchildren will keep as an hierloom not sell at a garage sale.

While it is possible to make some amazing art using only one type of material, the decision to use multiple materials in the same mosaic tends to stimulate the imagination, often in unexpected ways, in ways that leave the artist wanting to make a series of mosaics to capture just a mere fraction of what might be possible. This is because mosaic is dimensional. The artist might begin by thinking only in terms of the image to be rendered, but merely by handling the materials, the curious mind can’t help but think of what might be.

Troi O’Rourke’s fabulous Struttin’ Peacock is a great example of how tile of different thickness can be used in the same mosaic. Note that the fact that the surface isn’t flush is not a problem. To the contrary, the slight changes in elevation add a whole new dimension (literally) to the mosaic and help to set off the different fields of color.

Playing With Patterns

With mixed materials, there are differences in texture, size and shape (in addition to color), and with found objects such as seashells and artifacts, there is the significance of what those objects actually are in real life. And then there are all the different ways in which the materials could be arranged or grouped to contrast each other. The materials really do present an infinite regress for the artistic mind. I have gone into the studio very focused on a very specific design only to spend the entire session playing with different arrangements and variations. Sometimes I think I could live to be a thousand years old and not be able to complete all the designs I have already thought about. Thus is the nature of mixed-media mosaic art.

Groupings of Similar Items

Susanne Sorogon’s dragonfly is more of a departure from naturalistic rendering and makes greater use of mixed-media materials: beads, geode slices, millefiori, decorative tile and stained glass. Again, notice that the wings are not merely space to be filled but are used instead to play with patterns and groupings. The warm honey background and the intense blues of the figure make for a very effective contrast and are further proof of Sorogon’s skill as an artist. Note that this mosaic is ungrouted.

Below are some examples of mosaic portraits and impressionistic mosaic artwork with a discussion of how to create photo-realistic images in mosaic.

Frederic Lecut

As with painting, most of the work of creating a photo-realistic mosaic image is making sure the colors used reasonably match those of the model being depicted. In painting this can be done conveniently by mixing pigments. In mosaic this can only be done by sourcing different materials until you find what you need, which can be frustrating even with the aid of sample boards and online suppliers. Natural stone only comes in so many colors, and different brands of glass mosaic tile are only made in so many colors because it is produced as a building material and not really as an artist’s palette.

Artists frequently solve this problem by using “mixed media” and combining different materials such as stone, glass and ceramic in the same mosaic. Frederic Lecut of Mosaic-Blues.com is a master of this aspect of mosaic. His mosaic portraits shown here are made from multiple types of stone, glass, porcelain and colored mirror, some of which was sourced from recycled building materials.

Lecut says that the differences in thickness were not an issue for him because he works with the mosaic upside down in a reverse method. He pours concrete on top of the back of uneven mosaic, which fills in any differences in thickness, and then sticks a backer on top of the concrete. It is only later when he flips it over that he gets to see the finished mosaic.

Note that most novices prefer to work directly on a flat backer where they can see the mosaic as it is being created. This requires that the artist either cut their material to the same thickness or accept that the finished surface of the mosaic will not be flat.

Susanne Sorogon

Susanne Sorogon’s work is very sophisticated in that she subtly incorporates mixed-media elements (glass gems, accent tile, etc.) in mosaics that are photo-realistic. Many experienced artists would be capable of making an abstract mixed-media mosaic and a photo-realistic mosaic, but few would be capable of doing both in the same mosaic. One is reminded of the painterly flourishes that define the New Realism of contemporary painting, where the intent is to depict the model naturally, yet still make the paint itself interesting as it is in abstract painting. I particularly like Susanne’s use of upside down tile in the Motorcycle mosaic and how the embossed patterns on the backs of the tiles suggest asphalt that has been textured with non-slip divots, which is typically seen in the turns of race tracks, though conspicuously absent from the photo she used as a model.

Harjeet Singh Sandhu

Harjeet Singh Sandhu’s mosaic portraits of former New York Mayor Michael Bloomberg and 12th-century Sufi preacher Baba Farid Ji are well done, but what makes them amazing is that they are made from ordinary 3/8-inch vitreous glass mosaic tile, which is only available in a limited number of colors. In fact, at the time Sandhu made these mosaics, many of our normal colors were out of stock! Note that Sandhu was able to use this limited color palette to render two completely different skin tones in a realistic way. For that reason, I consider this pair of mosaic portraits to be something of a tour de force.

What to use for a backer is determined by how the mosaic will be displayed. For example, you could use a piece of sanded plywood as a backer for a small mosaic plaque or trivet, but you could NOT use plywood as backer for a mosaic floor because wood is compressible. Similarly, you could NOT use plywood as a backer for an outdoor mosaic or wet mosaic because plywood warps over time due to changes in humidity.

We have some additional recommendations for choosing a backer based on how the mosaic will be displayed.

Concrete Backer Board

The best all-around mosaic backer is concrete backer board, such as that used in bathrooms as the sub-floor for tile floors. Concrete backer board is cheap, cuts easily, comes in 1/4″ and 1/2″ thick sheets, and is available at almost any building material store. Drywall can be removed easily and replaced with a sheet of concrete backer board. The 1/2″ thickness is recommended for floors, and we only use the 1/4″ size when laminating it to plywood.

Using Concrete Backer Board for Wall Art or Plaques

A small piece of concrete backer board can be used to strengthen a piece of hanging wall art or a plaque. 1/4″ backer board can be laminated to a piece of plywood and then the edges sanded with a belt sander (wear a mask!) to make the sides look even. The backer board will provide a rigid and waterproof layer for the mosaic to rest on while the plywood behind it can be used to anchor the screws in that are needed for the hanging wire.

Mosaic artist Natalija Moss began this mosaic by laminating a piece of 1/4″ backer board to a piece of plywood. She used Weldbond mosaic glue and some clamps to laminate the plywood to the backerboard over night. Then she drew the pattern for the mosaic using a marker onto the backer board side of the piece.

Using the direct method, Natalija then started cutting and gluing pieces of stained glass directly to the backer board surface. Backer board may bond to the glue more quickly than other surfaces such as plywood, so make sure you have your pieces exactly where you want them or you may have to scrape them off with a flathead screwdriver which could damage nearby tiles, especially stained glass. Always wear safety glasses when mosaicing, but especially if you find yourself scraping off tiles.

The finished piece. There are two screws in the back of the plywood with a hanging wire tied to them. The plywood behind the backer board is about 1/2″ thick so she used short screws so as not to penetrate the backer board and damage the mosaic. It is also possible to cut a keyhole slot using a plunge router, but that should be done at the beginning before any glass is put down.

Durable, Strong, Inflexible, and Clean

Mosaic backings should be durable, strong, inflexible and clean.

Durable

Durable means resistant to water and moisture. Over the years, humidity in the air can turn plywood and particle board into splinters. Long before this happens, the tiles will begin popping off as the plywood warps. MDF and particle board swell and disintegrate with humidity as well. Avoid using wood products of any type outdoors. If you have to use wood outdoors, then use marine plywood, and make sure you paint the undersides and side edges with multiple coats of exterior paint and seal the finished mosaic.

All that being said, plywood can be used for dry indoor mosaics such as small plaques, picture frames and mirrors. If you make an indoor mosaic picture on plywood larger than 2 feet wide, then you should still paint the underside and sides to keep humidity from warping the plywood over time.

Strong

Mosaic materials are heavy, no matter if you are using stone, ceramic or glass mosaic tile. Grout is concrete. The weight of even one square foot of mosaic can be heavy. This means that not only your backer must be strong but also your points of attachment. (Never hang a mosaic from a single nail like a painting.) Mosaics made on thin panes of glass are also not recommended, especially glass table tops.

Glass table tops can sometimes be replaced with a sheet of concrete backer board if the table is strong enough to support the weight. (Never create a safety problem by gluing heavy mosaic materials to a glass table top.) The table should have a wide enough base so that the mosaic doesn’t make it “top heavy” or otherwise unstable. The table should also support the concrete backer in the center and not just on the edges. If your table does not have support in the center, consider bolting or welding a piece of angle-iron across the center.

Inflexible

Grout and mosaic tile are inflexible. If they are mounted to a backer that flexes even slightly over time, the grout and tile will crack and pop off. Mosaic backings for floors should also be incompressible. This is why concrete backer board is used beneath tile floors instead of plywood.

Note that plastic and thin sheet metal fail all three of the above criteria, but especially the requirement to be inflexible. Plastic and sheet metal also pose additional problems with bonding securely to glue and grout.

Clean

Walls and floors made from concrete, stone or masonry are obvious choices for mosaics, but even these ready-made backers should be scoured to remove paint, sealants and dirt, and you may need to plaster them smooth with mortar before starting the mosaic.

It never hurts to take a wire brush and scour a surface before you attach tiles to it. Nothing is worse than putting days or weeks into a project only to have it not hold up very well. It only takes a little dust or a little grease or a little paint to cause tiles to pop off within a few years or even months. How do you know that concrete wall doesn’t have an invisible pore sealer on it? You don’t. Take a wire brush and scour it!

If your surface is large, such as for a mural, then use a power tool called an angle grinder with a rotary wire brush. (Wear gloves and a face shield, especially if you haven’t used one before, because things like angle grinders and belt sanders can take the hide right off of you.) You can rent power tools at places like Home Depot, or you can ask your favorite handyman or handywoman to scour the wall for you. The point is that this type of surface prep can be done with little effort and is worth doing because it might determine whether or not your mosaic lasts more than a year or two.

Contemporary floor mosaics usually take the form of accents such as mosaic medallions and mosaic borders instead of the larger pictoral designs that covered the entire floors of ancient Roman houses. The contemporary mosaic accents are integrated with the existing flooring material, which is usually larger tiles of marble or ceramic. These limited area designs are more practical for the simple reason that most of the floor is covered with furniture, and it only makes sense to mosaic the small part of the floor where it will be consistently visible. That being said, I would absolutely love to have a customer email me pictures of a full floor design.

Mosaic Medallion

The mosaic below is a beautiful example of a compass rose medallion made by our customer Caroline Lahman from the tumbled marble mosaic we sell. I’m particularly impressed with the professional quality of the work Caroline did, and the fact that she actually took the time to photo-document the work in progess with publication-quality images, which is something I usually fail to do once I get rolling. The first step in making a mosaic medallion is to draw a pattern and tape it to a work table and cover the pattern with construction plastic or plastic kitchen wrap so that you don’t glue everything to your pattern. On top of this, fiberglass mesh is laid and the corners taped or tacked down securely. Although the pattern should be visible through the mesh, I find it useful to take a Sharpie brand marker and trace the design on the mesh directly just to make sure I can see it once things get a little messy. For most floors, water isn’t that much of an issue, but for shower floor and bathroom floor mosaics, it is something to think about. For these “wet” mosaics, I like to use only a drop of glue at the center of the tile when I attach it to the mesh. This leaves some of the tile uncovered by glue so that it can bond directly to the thinset mortar when the finished mosaic is mounted to the floor. The thinset mortar is much more water resistant than white PVA glues such as Weldbond. (That being said, Weldbond is fairly water resistant when fully cured.) Thinset mortar and grout are both concrete products that can stain porous materials like unpolished stone. To prevent this, the mosaic should be sealed before you grout it (and probably before you mount it because accidents can happen during mounting). The catch is that you don’t want to seal any surface where grout will need to bond, including the sides of the tiles. You only want to seal the top face of the stones. To do this, I use a small artist’s paint brush and carefully brush the sealer on the top face of the stone taking care to not let excess sealer run into the gaps between the stones. I use TileLab brand “Grout & Tile Sealer” for a normal seal. I use TileLab brand “Stone Enhancer & Sealer” if I want to slightly enhance/darken the stone colors (recommended). Both of these are available at Home Depot. Note that these products are invisible pore sealers and not an actual coating like polyurethane. The finished compass rose medallion is well integrated with existing floor and the color scheme of the room. Congratulations Caroline on the job well done!

Mosaic fireplaces are made by applying mosaic to the surrounding face, but not the inside of the fireplace itself. In fact, if the fireplace is actually used and not merely decorative, you probably shouldn’t mosaic the hearth (floor) in front of the fireplace because heavy chunks of wood and fire irons tend to crack and knock tile loose over time. That being said, porcelain tile and many varieties of stone are very hard and could be used for the hearth. The fireplace surround can be mosaiced with a variety of materials including glass tile.

Brick and stone should be plastered over with thinset mortar to smooth the surface in advance of actually applying the mosaic. Alternatively, 1/2 inch concrete backer board can be mounted over the existing fireplace surround as a backing for your mosaic.

For mounting the tiles, a white PVA adhesive such as Weldbond or thinset mortar should be used. I have written a page for using thinset mortar for detailed mosaic art, but for larger tiles, the thinset could be spread with a 1/4 inch notched trowel, and the tile pressed into it relatively quickly as is typically done with bathroom tiling.

A Whimsical Fireplace Mosaic

The fireplace mosaic below is a whimsical design made by my friends for their ice cream shop, which was located in a restored Victorian house in Decatur, Georgia. The color choices and motifs are in keeping with the kid-friendly theme of their shop.

An Outdoor Fireplace Mosaic

For outdoor mosaics subject to rain, humidity and freezing temperatures, thinset mortar should be used instead of adhesive to mount tiles. Thinset is a sticky concrete product that contains polymers for added strength and adhesive properties. We usually use it for grouting our outdoor mosaics because it is stronger than grout, and it will be the same color as any thinset that squeezes up between the tiles from when they were attached. We have successfully dyed thinset with concrete dye without any noticeable loss of strength or adhesion. Concrete dye and thinset are sold at most building material stores.

The fireplace below is actually an outdoor pizza oven, based on the wood-fired Italian variety, and the mosaic is on the hearth in front of the oven. The oven and the mosaic were made by one of our customers and her boyfriend in his backyard. “I Cinquanta Gradini” means “The Fifty Steps” in Italian, a reference to the 50 steps leading up to the house and oven.

Mosaic Tile is cut with a specific tool based on the type of material. Using the wrong tool wastes a lot of tile and is dangerous.

What tool should I use to cut which material?

Glass Tile

Cut glass tile with a wheeled Mosaic Glass Cutter. This is okay for vitreous or recycled glass. Cutting glass tiles can create sharp edges, jagged edges, and edges that just don’t look right. The edges can be cleaned up with a Ceramic and Marble File or a Dual Grit Rubbing Stone.

Stained Glass

Stained glass can be cut into small irregular rectangles and triangles with the mosaic glass cutter. If you are trying to make long, straight cuts or curved cuts use a Pistol Grip Cutter to draw the line and then snap the glass with a pair of Running Pliers. It is also possible to wrap stained glass or china plates in old newspapers or magazines and hit them with a Chipping Hammer, which has tapered heads for more controlled breaks and less waste by crushing at the site of impact.

Ceramic

Ceramic tile and china can be cut with a Tile Nipper and sharp edges can be smoothed with a Dual Grit Rubbing Stone.

Marble, Porcelain, Stone, and Hard Dinnerware

For stronger or thicker ceramics and for stone, marble, porcelain, and hard plates or bowls a Compound Tile Nipper is recommended. The compound nipper has a lever mechanism which acts as a force multiplier. When cutting especially hard materials with the compound tile nipper, pieces are likely to fly out when the material is snapped. It may be helpful to cut underneath a rag or towel to catch the shards.

Other Safety Considerations

“Always use the right tool for the right job.”

When working on mosaics using the wrong tool can present a safety hazard or damage the tool. Use tools as instructed above, don’t use them for other kinds of materials.

For example, never use a wheeled mosaic glass cutter on ceramics and dinnerware. Some kinds of dinnerware are among the hardest materials known to science. The wheeled blades can shatter and snap violently.

Also, you should never use a regular tile nipper on glass. Too much tile will be crushed and wasted.

Safety Glasses with Side Shields should be worn when cutting mosaic tile. Other people in the area should definitely wear safety glasses as well. Chips tend to fly away from the tool and out towards any people facing it.