People ask me about mosaic mannequins from time to time, and usually it is which adhesive to use for attaching tile to an old used mannequin they bought at a thift store. I also get questions about where to find a mannequin to use as a mosaic base, and I could only suggest eBay, garage sales, thrift stores and places the asker had already tried. Thankfully Judi Townsend at Mannequin Madness has let me know that they sell new and used mannequins online.
Mosaic artwork can include rough textural elements that would be impractical in architectural tiling such as a shower wall, which needs to be smooth for cleaning and safety. Note that smooth does not mean flat. You can have textural elements in an architectural surface, but they need to be rounded and not jagged. (Cheese-grater walls in the shower or even your hallway would be problematic.)
For the past few months or more, I have been meaning to create a mosaic which uses cut pieces of tile mounted on their side so that I could demonstrate how a “hand-cut” smalti look and feel could be created with ordinary molded mosaic tile, which is significantly cheaper than smalti. But work and other art projects kept getting in the way, until finally one day out of the blue artist Dee Ruff emails me some pictures of her work, and they illustrate exactly what I had in mind!
Mixed Media and Texture
Dee’s “In the Garden” mosaic really caught my eye because I have always been drawn to mixed-media mosaics and mosaics where the work lines of the background interact with figurative elements in the foreground. This mosaic has both. Plus as a subtle color wash gradient in the background. Plus a hand-cleaved texture made from molded recycled glass tile that was cut and mounted on edge. (It was almost as if this mosaic were made to order for me. Imagine my surprise when Dee emailed it to me.)
Dee says “in the Garden” is one of her favorite pieces. Note that the flowers are made from ceramic figures by Atlanta-based artist Martha Coursey, who does amazing work. I like how the smooth glazed ceramic pieces contrast with the rough cleaved texture of the sky.
Backers, Substrates, and Mounting
Dee makes her panels from recycled expanded polystyrene (Styrofoam) covered in alkali-resistant fiberglass mesh and multiple coats of thinset mortar colored with concrete dye. The “hollow” core makes the substrates lightweight, and the skin of thinset and mesh makes them strong and tough (impact resistant). Dee says that she builds the mounting hardware directly into the skin so that it is anchored by layers of thinset reinforced by fiberglass mesh.
Dee uses the Wedi brand of hardware, but brass picture hanging rings sold by building material stores should work, provided you use the heavier gauges. Note that no mounting hardware will be strong enough if you hang them on a nail in drywall, which is weak and fails easily. Nails or screws for mosaics and paintings of any size should go through the drywall and into the stud inside the wall (use a stud finder) or in the crown molding at the top of the wall with a hooked rod hanging down.
Note the safest and most robust mounting system is probably the French cleat. See Natalija’s Instructions for French Cleat Mounting.
More Of Dee Ruff’s Art
Dee Ruff currently has work available at the The Mosaic Love Gallery in Jonesborough, Tennessee. Dee’s website is Black Cat Mosaics, and she has some interesting multimedia mosaics and collaborations online there.
A few years ago, Karen J created a mosaic bench in her backyard using mining debris (large stones), cement, and chicken wire to form the base, which is similar the methods we recommend in our instructions for creating bases for outdoor mosaic sculptures. Karen modeled her bench after those made by the great mosaic architect Gaudi in Park Guell in sunny Barcelona, and she used brightly colored ceramic tile just as Gaudi had used. The problem is that Karen’s backyard is in Colorado, and so her mosaic experienced many long and hard freezes that a mosaic in Barcelona would never see.
Ceramic Tile Is Vulnerable To Freeze Damage
Glass mosaic tile is non-porous, and so water cannot seep in and freeze and crack it, and so glass is preferred for outdoor use, as is porcelain tile for the same reason. On the other hand, ceramic tile tile is very porous and soft, and so water can penetrate it (through tiny cracks in the glazing). Once this water freezes and expands, it cracks the ceramic tile and often causes the face of the tile to flake off.
In the photo above, you can see how some colors were more resistant to freeze damage than others. This difference was not due to the color but to the variety of the tile: some brands of ceramic are harder and less porous than others. Also, some brands have thicker glazes, and that can also affect how permeable the tile is to water.
Preventing Freeze Damage
You can minimize freeze damage by sealing your finished mosaic with multiple applications of a tile and grout sealer from your local building material store. Avoid ordering sealers online during winter months because water-based silicone sealers ruin if they freeze during shipment. You should also clean and reseal the mosaic each fall. Small mosaics such as mosaic stepping stones can be brought inside for the winter.
Mosaic Fireplace and Oven Surrounds: The Basics
A couple of years ago, I wrote a page explaining how glass, ceramic, and stone tiles can be used for mosaic fireplace surrounds and how the tiles should be mounted with thinset mortar or white PVA (polyvinyl acetate) adhesives such as Weldbond. But we are talking about the SURROUNDS, not inside the firebox. For inside the firebox, your need to use refractory materials (brick or stone) that can resist combustion temperatures. For the hearth, the issue is not temperature resistance so much as impact resistance: It doesn’t make sense to use glass tiles that are easily cracked by a metal poker or small tiles that are easily knocked loose. Stylistic concerns should never outweigh performance and durability, else the work won’t look good for long.
Problems with a Mosaic Pizza Oven
Recently, artist Kristina Young emailed me concerning a problem she was having with a mosaic she installed on the outer surface of an Italian pizza oven. The problem was that the mosaic was cracking over the door of the oven, and that caused me some concern because that should not happen with traditional fireplaces and pizza ovens constructed with brick or stone, and I have been telling people for years that there was no reason why they could not put mosaics on these surfaces in spite of the heat. Had I overlooked some basic technical principle and made recommendations that could ruin hundreds of people’s projects? The engineer in me became completely paranoid, and I could not wait for Kristina to email me back with answers to my initial questions.
Spoiler Alert: The good news is that the cracking is reparable and that the cracking is by the iron frame of the oven door, not the masonry elements of the oven itself, which means that there is no reason to expect similar problems with traditional fireplaces and ovens that are made from all stone or brick or concrete.
The Case of the Cracking Mosaic
When Kristina first contacted me, she was concerned that the cracking might have been caused by heating the oven not long after the mosaic was completed. That is a potential issue because thinset mortar takes time to harden, and like concrete, it hardens by bonding moisture not by drying out. (Concrete, mortars, grouts, and other portland cement products will be soft and crumbly if they are dried out by heat or dried air. They need to incorporate the water mixed into them, not have it removed artificially.)
Humidify, Don’t Heat
I don’t think that the oven was heated prematurely or that premature heating caused the cracking. The crack is location specific, and if the mortar was artificially dried out before it could harden, then the problem would be seen all over the mosaic in the form of cracks and missing tiles. That being said, I would avoid heating fireplaces and ovens for several days after a mosaic has been applied to them and grouted. The usual practice is to run humidifiers near a new mosaic to protect them from AC or central heat –not build a fire under them!
Except for the notable exception of ice, most materials expand when they are heated. (Water expands when it freezes, and that is why ice floats: it is less dense than the water beneath it.) The problem with thermal expansion is that materials expand at different rates, and metals like iron expand more rapidly than stone, brick, and concrete. Kristina had already told me that the crack started on the front of the oven just over the door, and so as soon as she sent me a picture of the oven showing that the door had an iron frame, it was obvious to me why the crack had started there: The glass and mortar mosaic expands at roughly the same rate as the brick and concrete oven underneath it, but the iron door frame and the other iron structural elements expand even faster. They push the mosaic up like a shell on the outside of the oven, and when the oven and frame cool back down and contract, the crack appears.
The Right Repair Materials
An “expansion joint” spontaneously forming in the middle of your mosaic might have most people panicking and thinking of repairing the crack with a flexible material such as caulk. Caulk is problematic because it will not age well. It will yellow and shrink and crack. It will look more and more like the synthetic material that it is, a material that looks out of place on tile, a material which does not age.
Grout could be used to fill the crack. After all, grout is the concrete product that is used to grout gaps between tiles in the first place. However, thinset mortar is a better choice because it is harder and tougher and more adhering than grout,, and it can tolerate slight displacement (movement) while grout cannot. In fact, it would have been best if the entire mosaic had been “grouted” with thinset. I suspect that heating and cooling the oven in cycles over time may cause other cracks to appear or reappear, and these should have thinset rubbed into them as needed. Hopefully any new cracks or reappearing cracks will be smaller, but in any case, thinset is better equipped to withstand the stresses of expanding and contracting than grout.
Aesthetics and Authenticity
Think of high-end restaurants in reclaimed urban warehouse spaces: the exposed beams, the plaster chipped away in places to reveal the stone walls underneath, the different architectural elements like fire doors and hoists deliberately left in place to call attention to the space’s past industrial use.
To me, one of the more interesting things you can see in the mosaics of Mexico and the Mediterranean basin are the repairs that have been made to these over the years following earthquakes and other damage. I’m not thinking of the repairs that were made in modern times by archaeologists or professional conservators sparing no expense to make the mosaic look as if the damage had never occurred. I’m thinking of repairs made in the distant past by inexpert hands or by people with limited access to materials. I’m thinking of repairs like mortar-filled voids and replacement tiles of not-quite-the-right color and how you can sometimes see a series of these inexact repairs apparently made at different times in response to different injuries. To me, these inexact repairs more than anything else give me a sense of how ancient the mosaics are and how much history they have witnessed, endured even: earthquakes, fires, wars with slings and arrows, wars with bullets and bombs.
A large part of the ethos of mosaic art is it being an enduring relic of the past. If I were wanting to design a mosaic to look like an old relic, I might consider deliberately including mortar-filled voids and cracks to simulate past damage or maybe re-mosaicing some of these regions with coarser tile. With that in mind, is a crack appearing in a new mosaic in an Italian or Mexican restaurant a problem or a windfall? I’m thinking not. I’m thinking of the kid who deliberately scuffs up his new baseball glove so that it doesn’t look the unused glove of a rookie.
Artist MC Holt-Evans of Nashville recently made a mosaic sculpture very much in keeping with spirit of The Music City, and her mosaic guitar is worth taking a look at, especially if you are considering making a mosaic on an improvised base such as a musical instrument or a piece of furniture. The instructions below could be adapted for using other household objects as a base.
Mosaic Sculptures on Improvised Bases
Mosaic sculptures that use household objects as their base aren’t anything new. For example pique assiette (broken plate) mosaic furniture is fairly common, as are mosaic gazing spheres made from bowling balls. (Note that my article on gazing spheres explains why hard polystyrene makes a better base than a bowling ball.) However, a guitar can be a particularly challenging choice of mosaic base for several reasons: The shape is complex and curved, and part of it (the neck) is long and thin and has a lot of corners. The wood of the guitar’s sound box is thin, and yet it has a thick layer of lacquer that must be removed before adhesives and grout will bond to it.
Prepping the Guitar
A medium grit sandpaper (120 grit) can be used to take off any lacquers or sealants. As always, wear an N95 rated dust mask for doing this type of work. (The N95 dust masks are cheap and readily available at a building material or hardware store.) I don’t recommend wet-sanding a guitar because you want to minimize its exposure to moisture until you get it sealed because the wood is thin and easily warped by moisture.
Are you going to want to put the strings back on the guitar after it is mosaiced? Probably so, and that mean you need to take into account the thickness of the tile you are adding to the surface and raise the nut fret that separate the head from the neck. Use a hard wood for this such as bass (the wood used for sewing boxes and buttons) and not some soft wood like balsa.
When you reseal the guitar with a water-based primer, you should apply two thin coats instead of one heavy one. To seal her guitar, Holt-Evans used an acrylic primer called Zinsser’s Bullseye 1-2-3 because it was recommended by an artist who works with mosaic guitars. Weldbond adhesive could also be used to seal/prime a guitar, and it might be the better choice because it is the adhesive that will be used to attach the tiles, and thus you wouldn’t have to worry about how well the adhesive and primer bonded to each other, but you would still need to give the sealing coat at least a week to dry out completely and fully harden before you tiled on it. Holt-Evans reported that she left coarse brush strokes in the sealant. This improves the bonding of adhesives and grout.
Using What You Have on Hand?
Be careful selecting a primer at random because Weldbond might not bond to some of them, definitely not oil-based materials. You want an acrylic, something like an artist’s gesso and not a latex house paint. PVA’s like Weldbond won’t bond to the vinyls and other binders in some house paint. Using what you have on hand isn’t necessarily being frugal if it doesn’t last nearly as long as it would have with the right stuff.
Mounting the Tile
Partially Crushed Liquor Boxes
Use partially crushed liquor boxes to cradle the guitar or sculpture while you work on it. You can rearrange the boxes to re-position the guitar as needed so that whatever part of the curved surface you are working on is facing up.
Brush on the Adhesive and Let It Get Tacky
If you are having problems with tile sliding around, use a small paint brush to spread the Weldbond onto the surface and allow to sit for a few minutes and get tacky before you add the tile. Depending on how dry or moist your air is, this can be about 15 minutes, perhaps much faster if it is dry midwinter air and the heater is running. Remember, if you let the glue skin over too much, then it won’t bond to the glass as well.
Dental Picks and Cotton Swabs
Dental picks (or tooth picks) are invaluable for adjusting the positions of tiles without contaminating your fingertips. Cotton swabs can help clean up messes with precision and not move tile out of position. Tip: Don’t thow your wet-glue swabs into the trash. Instead, let them dry out and peel the dried glue off them next session and get another life out of them.
Grouting Studio or Bench Space
I like to grout outside on a patio or some place that can be hosed off. You can use drop cloths indoors, but you still have to be relatively neat, or you will track sand on the floor and ruin it. Grout and thinset mortar are concrete, not paint. That being said, grouting inside can be done without making a mess and is routinely done by mosaic artists. A plastic folding table or a table covered in construction plastic from the building material store is ideal for a project that might require multiple sessions to grout.
Black grout makes color stand out more. All grout colors are lighter when the grout hardens, especially black grout. Black grout is usually jet black when mixed up but hardens to a charcoal gray or lighter. Pure white grout makes a mosaic look like a summer camp project.
Thinset Mortar vs Grout
I prefer thinset mortar instead of grout for projects like these. Thinset has an adhesive polymer in it that makes it strong and resistant to impact. Compared to ordinary concrete and grout, thinset is a lot less likely to crack and crumble when dropped. However, thinset contracts slightly as it cures, and so you might observe hairline cracks when used on a three dimensional object that can flex slightly, such as a wooden guitar. Like grout, thinset mortar can be dyed with concrete dyes.
Grouting something like this is best done in multiple sessions. Unlike a mosaic chair or desk, a guitar has multiple places where special are has to be taken in order to not soil or clog some detail. A guitar has frets and working pegs and a saddle and a sound hole to take into account. Painter’s tape can be used to protect the bare wood inside the sound hole. Use crushed liquor boxes to cradle the guitar in different orientations while you grout it.
The color of a grout can look different if different amounts of water are used to mix up different batches or if they are misted differently. Try to mix up and handle your grout in a consistent way.
Holt-Evans started by grouting the back of the guitar because it was the largest flat area with no obstructions and therefore the most straightforward surface to be grouted. When she grouted the back, she continued the grout over the sides so that there wouldn’t be a grout seam right at the corner because corners are vulnerable places and subject to many impacts.
The head and neck were each done in separate sessions, and for both of these elements, Holt-Evans did not take the mosaic and the grout around to the sides and backs. Only the top faces were covered, and so this meant that the grout had to be tapered off to the corner.
The front of the guitar was done in a later session because of the detail work required to get the grout tapered to the edge of the sound hole. The grout was carried down over the side to join the grout from the back on the sides.
To prevent a hairline crack where new grout meets the old, you should moisten the edge of the old grout with a little water on a cotton swab before grouting. This keeps the old grout from sucking all the water out of the new grout before it has a chance to harden.
Artist Lyn Richards sent me some pictures of the mosaic bird bath she made this past summer, and it is worth showing off. The floral design and the colors used in the mosaic were inspired by Van Gogh’s painting “Irises.”
Material List for a Mosaic Birdbath
To make a mosaic bird bath such as this, you could use a ready-made concrete bird bath from a lawn and garden center, or you could make an original concrete sculpture if you are looking for something with a less conventional shape. Lyn used a ready-made concrete bird bath that came in two sections: a base column and a bowl.
Thinset Mortar and Tools
Thinset mortar should be used instead of adhesive for attaching the tile. A complete list of tools and materials for mixing thinset and for applying it is given in my instructions for using thinset mortar with glass tile. (Note the instructions were written for doing extremely detailed work, so I might make thinset seem much more difficult to use than it really is.) I have also written a page for how to keep your hands clean when using thinset.
Glass Mosaic Tile
Glass mosaic tile in non-porous and so water can’t get inside it and freeze and crack it all to pieces. This makes glass superior to stone and ceramic tile when used outdoors. You can use any of the glass we sell. Lyn’s mosaic was made from different brands of 3/4 inch vitreous glass tile, metallic glass tile. iridescent glass, and stained glass.
To find out how much tile you need, you can divide your shape into component surfaces and use our mosaic tile estimator. What do I mean by component surfaces? For estimation purposes, Lyn’s bath can be thought of as cylinder topped by a disk. The surface area of the cylinder is A = D*Pi*H, where D is the diameter, and Pi is 3.14, and H is the height. The surface area of the disk is A = Pi/4*D*D. Note that this time D is the diameter of the bowl and not the pedestal base. Remember to multiply the surface area of the disk by a factor of 2 because there is a top and a bottom.
As always, remember to inflate your estimate by 5 to 10% to account for cutting scrap and to provide a cushion for error in your estimates. I have always found that it is much better to have tile left over than it is to not have enough. Suppliers sell out from time to time, and the next manufacturer batch might not match what you already have, or at least match exactly. Also, leftover tile serves as inspiration and material for future projects.
Finding and Transferring Patterns
Lyn used Van Gogh’s painting “Irises” for her pattern. She drew the outline of the shapes (blades and petals) onto the concrete using a pencil, and then she went over that drawing with a black Sharpie marker when she was sure she had her lines correct. This is recommended: Don’t use the marker until I work out my lines by trial and error using a pencil. If your pencil drawing gets to be a mess and you need to start over, you can “erase” it by wet sanding it and wiping it off with a rag.
Choice of Colors and Visual Interest
Note how Lyn used multiple shades and hues of green to make the blades of the iris leaves instead of using just one type of green. This creates shade and depth and visual interest and makes all the difference in the world. Monochromatic color fields are boring, and they take just as long to tile as a more interesting mix of colors. Note the solitary pea green blade of new growth and how it stands out from the other leaves, which are a mix of darker and bluer greens. Similarly, the petals of the irises are made from multiple cyan blues and ultramarine blues instead of one color, and this makes them more lifelike and more visually appealing.
Andamento and Visual Interest
The background of a mosaic is an opportunity to add visual interest to the scene and should never be “bricked” up like the tiled wall of a shower. Andamento is the visual flow of a mosaic created by arranging the tile in rows, and it can make the background of your mosaic as visually interesting as the figures in the foreground.
Observe how Lyn used multiple related hues for the background instead of one color. Also note there is not a single whole tile mixed in with all these cut pieces. Why not? A uniform square would stick out like a sore thumb among all the irregular pieces.
Cutting and Attaching the Tiles
Thinset is concrete that hardens over time. I can usually get three hours out of a batch, and I often work in sections, usually completing about 1 or 2 square feet per session, depending on how detailed my work is. Lyn found it useful to have her tile cut up in advance of a session, but you can always make incidental cuts as needed while you are attaching tile. Again, my thinset instructions explain the details of how to handle and use the mortar to attach tiles. Tip: partially crushed liquor boxes make great cradles for holding heavy pieces of stone and concrete while you tile them.
Removing Sharp Edges
A marble file or a rubbing stone can by used before the tile is mounted to remove any sharp edges. After the tile is mounted, it is a little more difficult to remove sharp edges, but gently rubbing the surface of your mosaic with a rubbing stone can help a lot.
Before grouting, you should clean off any excess thinset from the face of the tiles. Scraping this off will also make any loose tiles fall off so that you can reattach them before grouting. You should wait a day or two before grouting to let the thinset harden. Black grout is best for making your colors stand out. Lyn used a combination of black, gray, and brown grouts, and she blended these to get the exact color she wanted. A few days after your grout hardens, you should buff all the grout haze off and seal the finished mosaic with multiple applications of a silicone-based tile and grout sealer, such as available at any building material store.
Please email us pictures of your Christmas tree ornaments made from our mosaic ornament bases. I would really like to receive a picture of one made to look like a globe of the Earth. I think a globe ornament would look spectacular, especially in mosaic, but I haven’t had the time to make one myself due to all my other art projects.
Remember to order your mosaic ornament bases early because we often get large orders from groups that completely exhaust our supply of hard polystyrene spheres.
Each ornament base is only 29 square inches (or 0.2 square feet) of surface area, so it doesn’t take too much tile to cover one. Just one bag of the 12mm Elementile Recycled Glass Mosaic Tile is more than enough to make an ornament. Depending on how you cut and space the tile, you only need between 100 and 125 tiles to cover one ornament, and each bag of 12mm Elementile contains about 185 tiles.
There are two options for bases for making a mosaic sculpture for your lawn:
- Buy an unfinished concrete sculpture from a lawn and garden center or a store that specializes in concrete lawn sculpture.
- Make your own concrete sculpture using cement and chicken wire and pea gravel and similar reinforcing materials as discussed on various websites found by searching Google for “concrete sculpture” or our page for how to make concrete mosaic sculptures.
Note that my page focuses on a large structural base I was making at the time while some of the other websites have better pictures of how to crumple up chicken wire to make smaller figurines. However, the Internet contains a lot of problematic advice about hypertufa and other practices, so make sure you read my caveats below.
Each of these options has advantages and pitfalls that are important to consider before deciding which route you will go. Either way, following best practices to prevent moisture penetration is critical for ensuring the longevity of your mosaic lawn art.
Purchasing A Factory-Made Base
A factory-made base purchased from a lawn and garden center will be identical to all the other pieces made from the same mold, but there is obvious the advantage that you can start mosaicing immediately without having to make the base yourself, which is a complete project in itself and tends to be more labor intensive than expected, unless the artist has worked with concrete before. Also, you can make the generic base into an original work of art by how you tile it, as demonstrated by the artwork by Lyn Richards featured on this page.
Sealants Can Interfere With Bonding
If a drop of water soaks into the surface of the concrete, there is no excess sealant present, and the thinset mortar used to attach tiles should be able to bond securely.
Sometimes you can find factory-made sculptures that have been drenched in sealants, and these can interfere with thinset’s ability to bond to the concrete securely, and tiles could fall off over time. If a drop of water beads on the surface of the sculpture (similar to how water beads on a waxed car), then you know the sculpture is coated in a sealant that should be removed before mosaicing. To remove the sealant, scour the surface with a stiff wire brush of the type used to clean welds (the wires are stiffer and more coarse than those on most wire brushes used to clean barbeque grills).
Beware Of Lightweight Concrete
Sometimes factories will mix expanded perlite or other materials into the concrete to make it weigh less than regular concrete. This is fine in theory, but the expanded perlite is highly porous and mostly air and therefore readily absorbs water. This makes the sculpture highly vulnerable to freeze damage: water seeps in, freezes and expands, and then the surface of the concrete flakes off. If you find a sculpture that appears to be lighter than expected or has a softer or more porous look to it, then coat it all over (bottom included) with a layer of thinset mortar and allow that to harden before you mosaic on it.
Making Your Own Concrete Sculpture For A Base
Mixing up even 5 pounds of concrete can be labor intensive, and mosaic lawn sculptures of any size at all can require 25 to 50 pounds at least. As you might recall from mixing up grout, your arms feel it even with the small batches, and most people will find a drill with mixing paddle necessary to mix up anything over 10 pounds.
Several of the websites explaining how to make concrete sculpture emphasize the need to make the bases hollow or to use Styrofoam or harder varieties of expanded polystyrene to fill internal voids. This is good sound advice, especially if you make the surrounding shell of concrete structurally sound by reinforcing it with metal rods and wire.
Thinset Instead Of Regular Concrete
There are different concrete mixtures recommended on the various websites, some of which include glass fibers used to give the concrete the tensile strength it normally lacks. For my concrete sculptures, I used thinset mortar instead of regular concrete. Thinset mortar is like regular cement with sand, but it also has polymers for adhesion and tensile strength. I also mixed in fine pea gravel for additional strength and bulk. The pea gravel was sieved to remove larger pieces and added 1 part pea gravel to 2 parts thinset on a weight basis.
Thinset is more expensive than regular concrete, but it is so much stronger, and you don’t have to worry about whether or not it is adhering well to a bare wire frame. Also, if you have to add concrete to a large frame in multiple batches mixed in multiple studio sessions, you can be confident that the fresh thinset is adhering to the thinset that is already hard, and you can’t say that about regular concrete, which is likely to form a crack at the boundary.
Of course, the concrete sculpture recipes I saw on various websites recommended different latex additives that should be added to the regular concrete to make it be more like thinset. But my thoughts were why reinvent thinset from different components if I could simply buy thinset, which was actually cheaper by the time you factor in the additives. Also, instead of picking or sieving the larger rocks from a bag of concrete, I thought it made more sense to start with a bag of thinset (which contains no stones) and add the exact size of pea gravel I needed to ensure it fit into my wire mesh frame.
Hypertufa is synthetic version of a type of porous limestone called tufa, and it is popular for making custom planters because its porosity is good for plant roots and getting covered with moss and lichens. Hypertufa is made by mixing peat moss and perlite and sometimes other materials into concrete to make it porous and lightweight.
About half the post you see on gardening blogs repeat the mantra the hypertufa is completely freeze proof. The other half are asking for advice of how to prevent their hypertufa planters from mysteriously cracking (usually with an acknowledgment that they accept the official dogma that the cracking couldn’t possibly be due to freezing temperatures).
What I do know is that all other porous materials I have encountered in my experience with outdoor mosaics are highly susceptible to freeze damage: terracotta, unglazed ceramic, unpolished stone, etc. If it has small holes in it, even tiny microscopic holes, then moisture penetrates and freezes and cracks or flakes the surface.
I’m not sure why hypertufa would be any different. The peat moss and perlite are ready conduits for deep moisture penetration. I strongly suspect that hypertufa is so soft that the damage due to freezing and expanding doesn’t result in macro cracks right away, and thus people with weak reasoning skills assume it is freeze proof. Later when cumulative damage finally results in a crack, the crack is attributed to the anger of the hypertufa gods or something like that.
I strongly suspect that hypertufa is so soft that the damage due to freezing and expanding doesn’t result in macro cracks right away, and thus people with weak reasoning skills assume it is freeze proof. Later when cumulative damage finally results in a crack, the crack is attributed to the anger of the hypertufa gods or something like that. “I must have done something wrong in how I mixed up the hypertufa or cured it. It couldn’t be the freezing winter conditions.”
All that being said, hypertufa is fine for someone making a simple un-mosaiced planter and wants it to crumble away slowly like natural limestone. But if you are going to the time and expense of covering it with mosaic tile, then avoid hypertufa. If you want to make a lighter core from concrete mixed with perlite, that is fine, but cover the outside with a layer of thinset before you mosaic to ensure that the vulnerable porous material is protected from the risk of moisture penetration and freeze damage.
How To Mosaic A Concrete Lawn Sculpture
Like all outdoor mosaic and wet mosaic, the tile should be attached with thinset mortar instead of glue. Other than that, the instructions are more or less the same as our instructions for regular flat panel mosaics. I wrote some detailed instructions for using thinset mortar for mosaic art.
You can grout an outdoor mosaic with thinset instead of grout. Thinset is harder and more water-resistant than traditional grout, so it is probably better to use thinset for grouting. Thinset can be dyed with concrete dye. (Note that I am always talking about traditional powered thinset mixed with water and NOT the new epoxy-based systems with a liquid component). I use Versabond thinset in my work, and I have exceeded the dye manufacturer’s maximum recommended amount of dye in the thinset by a factor of 2 without affecting hardness or bond strength in any way that I could notice, but I am sure that it is possible to add too much dye depending on the brand.
Tip: Put cardboard on your work table to protect it from the weight and roughness of the concrete sculpture.
Tip: Rest the bottom of the sculpture on small blocks such as stone tiles or whatever so that you can mosaic and grout the bottom edge of the sculpture without the surface of the table getting in the way.
Tip: Consider sitting your sculpture on some plain concrete stepping stones when you install it in the garden by raising it slightly off the moist soil, you can greatly increase the life of the mosaic, especially the tiles near the bottom edge.
Tip: Use a pencil or marker to draw patterns on the surface of the sculpture.
Tip: Never use one color blue to make a color field when you could mix two similar blue colors to make the same field of color. It makes the element more visually interesting.
REQUIRED: After your grout has hardened for a few days, seal your finished mosaic sculpture with multiple applications of a tile and grout sealer following the instructions on the package. It wipes right off glass tile and only seals invisible pores.