Tag Archives: garden mosaic

Mosaic Concrete Lawn Sculptures

There are two options for bases for making a mosaic sculpture for your lawn:

  1. Buy an unfinished concrete sculpture from a lawn and garden center or a store that specializes in concrete lawn sculpture.
  2. 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.

Frog mosaic lawn sculpture

Frog mosaic lawn sculpture by artist Lyn Richards is an excellent example of how you can take a mass-produced concrete base and make it your own unique piece of art by how you tile it. Note how the artist used multiple green hues instead of one monolithic color field and how the greens contrast the reds and yellows, which are arranged in patterns that suggest motion.

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).

Butterfly mosaic planter

Butterfly mosaic planter by artist Lyn Richards was made on a concrete base, which are much more durable than terracotta planters. Note how the artist used the grout line to add even more detail to the butterfly’s wing. Also note how the black grout makes the colors look even brighter.

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.

mosaic bird bath

Birdbath mosaic by artist Lyn Richards. Outdoor mosaics on horizontal surfaces tend to have shorter lives as standing water penetrates between the tiles. Mosaic benches and birdbaths and other horizontal surfaces should be sealed with multiple applications of a tile and grout sealer to prevent this from happening. You should also consider cleaning and sealing these surfaces every year or two.

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

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.

Fish mosaic planter

Fish mosaic planter by artist Lyn Richards makes excellent use of glass gems as bubbles. Notice the mixed use of green hues in the seaweed and how the fish and weed are integrated and how they make use of contrasting colors from opposite sides of the color wheel (green and orange). The white makes these colors “pop” even more, as does the black grout.

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.

Mosaic Gazing Spheres

Mosaic gazing spheres are popular outdoor mosaic projects, and they offer a few simple advantages over mosaic-covered concrete lawn ornaments: They are lighter in weight and can be relocated more easily. Also, the mosaic gazing sphere can be adjusted in height easily by changing the height of the display stand used to support them. These are important points if you want to keep the mosaic prominently displayed as vegetation heights change throughout the season. (Think about annuals in flower beds and how high something like black-eyed susans can grow and even hedges can be an issue if you don’t have time to trim them regularly.)

I have instructions for making a mosaic sphere toward the end of this article, but I wanted to mention a few important points first:

How To Display The Gazing Sphere

Wrought iron planter stands that are relatively simple in design make the best supports for mosaic gazing spheres. The ideal type of stand is a circular ring with 3 or 4 legs. You can find these at many lawn and garden centers. Tip: Use a little bit of black electrical tape to wrap the metal ring in four places so that the glass tile doesn’t rest directly on the metal ring. It’s OK for the tile to rest on metal in theory, but eventually someone is going to pick the sphere up to inspect it and not be as careful as they should be in returning it to the stand.

Mirror Tiles

Ordinary mirror cannot be used without a special adhesive that prevents the silver backing of the mirror from oxidizing and turning black. This adhesive is oil-based and relatively expensive compared to thinset. That is why we sell a mirror tile that has a special coating on the back that allows the tile to be mounted with thinset, PVA adhesives and other mosaic glues without turning black over time.

Don’t Use A Bowling Ball

Many people email us asking how to use old bowling balls for making mosaic gazing spheres. Bowling balls make problematic bases for outdoor mosaics for two reasons:

  1. Bowling balls have been reported to expand in high temperatures and cause mosaics to crack and tiles to fall off.
  2. Thinset mortar does not bond to the polymers bowling balls are made from, and thus an epoxy adhesive or oil-based is required, and that means fumes, difficult clean up and shorter working times.

Either of these reasons would discourage me from using a bowling ball as a base even though I like to use recycled and repurposed materials as much as possible.

Where To Get A Hard Polystyrene Sphere To Use

Normal Styrofoam is too soft to use as a base, but there are harder varieties of expanded polystyrene that is ideal: strong, lightweight and bonds to PVA adhesives and thinset mortar. The Plasteel Corporation’s Smoothfoam website sells an 8-inch hard polystyrene sphere. The sphere comes in two halves that can be joined with the same Weldbond PVA adhesive or thinset that you use to mount the tile. Note that you should join the halves prior to mounting the tile, else you are likely to not mount the tile in a way that does not call attention to the seam. There are larger sizes available, but the 8-inch sphere is approximately the size of a standard bowling ball (8.5 to 8.595 inches).

How To Make A Mosaic Gazing Sphere

There is much about making a mosaic gazing sphere that is similar to making a mosaic on flat panel: Tile is attached to the surface using thinset mortar or a white PVA adhesive such as the Weldbond, and after this allowed to harden for at least a day, the mosaic is grouted by rubbing wet grout into the gaps between the tiles.

The Basic Mosaic Process

We have a page of illustrated mosaic instructions for more information about this basic process of attaching tiles and grouting. We also have a page about how to avoid grouting disasters.

Putting Your Pattern On The Sphere

You can draw the pattern of your design onto the surface of the sphere with a Sharpie marker or a pencil. Even if your design is as simple as an abstract pattern of swirls or rings, it helps to draw lines as a guide for each row of tile.

Make sure you position the tile in adjacent rows so that four corners are never lined up together. (You want to avoid positioning your tile in a grid similar to how showers are tiled.) Instead, have the gap in one row coincide with the middle of the tile in the rows to either side. This makes each row stand out, which helps each row suggest motion.

Decide Thinset Or Weldbond

Thinset mortar is generally required for outdoor and wet mosaics. White PVA adhesives such as Weldbond are generally reserved for dry indoor mosaics. However, Weldbond is water resistant when fully cured, and if the sphere is displayed on a stand where it cannot sit in standing water, then a mosaic sphere made using Weldbond could have an extremely long life, especially if it were sealed with a tile and grout sealer.

I have also come to accept that many people are intimidated by working with thinset because it has to be mixed up from powder form, cannot be stored once mixed up, and it is messier to use for a novice.

All that being said, if you want to learn how to do this professionally, or if you want to make absolutely certain that your projects last as long as possible, then you need to learn to use thinset, which isn’t that hard in my opinion. I wrote a page about how to use thinset mortar for mosaic artwork and a blog article about how to keep your hands clean when using mortar.

Decide Which Tile

GLASS is the best tile to use outdoors because it is nonporous and therefore impervious to moisture, and thus it is frost proof. Ceramic and stone have micro pores, and water can penetrate and freeze and cause the faces to flake off. Ever notice how the surfaces of terracotta flower pots start to flake off when left outside over the winter? That is what is happening.

Keep in mind that the Greek and Roman mosaics made from stone lasted because the climate of the Mediterranean basin is dry and relatively mild. If you want your outdoor mosaic to last in temperate and northern climates, use GLASS tile and then grout and seal it.

Each sphere has approximately 1.4 square feet of surface area, so that means you would need:

Of course those numbers assume a grout gap of 1/16 inch. With the 8mm tile, you might want them slightly closer together. Also, if you are cutting the tile, you might want to budget 5 to 10% more to account for cutting scrap.

Grouting And Sealing

Outdoor mosaics should be grouted and sealed. You cannot simply place the tile as closely together as possible. Water can find its way into the tiniest crevice or pore. Consequently, you have to leave a large enough gap (usually 1/16 inch) to ensure that the gap is wide enough to get filled with grout. (As ironic as it sounds, you have to leave a gap to ensure that the gap gets closed up.)

A few days after your grout hardens, you should seal the mosaic with a tile and grout sealer, which are invisible pore sealers that wipe on and wipe off. They aren’t coatings that form a clear layer over the surface. We use TileLab brand that we buy at Home Depot.

One Side At A Time

How do you glue tile to a sphere? One side at a time. Sit your sphere on a folded towel or cardboard box to keep it from moving or rolling as you glue the tile on the upper surface. Rotate the sphere only after the glue has started to set. If you are working carefully to ensure a uniform grout gap, you will probably be slow enough to ensure that the glue is hard enough before you have to rotate the sphere slightly to continue.

 

How To Mosaic a Patio Table

Replace Glass Top With Concrete Board

Glass-top metal patio tables can be used to make a mosaic table by replacing the glass top with 1/4 inch concrete backer board. The concrete backer board is roughly the same thickness as the glass top it is replacing, and it can rest on the rim of the metal table just as the glass top did. However, the thin concrete backer board can sag if unsupported, so marine plywood or pressure-treated plywood should be laminated to the underside of the backer board to stiffen it.

Note that the plywood should be slightly smaller in diameter than the concrete backer board so that it doesn’t interfere with the metal rim of of the table. Only the concrete backer board rests in the inside of the rim where the glass rested. If the plywood were to rest there, then the table top would be too thick and stick up above the rim instead of fitting inside it like the glass.

Steps For Replacing The Glass Top With Reinforced Concrete Mosaic Backer

  • buy 1/4″ concrete backer board from building material store.
  • measure glass top being replaced.
  • cut 1/4″ concrete backer board into a circle the same size using jig saw.
  • cut pressure-treated plywood into slightly smaller circle using jig saw with fresh blade.
  • glue plywood to concrete backer board using Weldbond or other PVA glue.
  • paint underside of plywood and its outer edge with multiple coats of outdoor paint.
  • insert table top into metal table base.

Repairing Edges of Concrete Backer Board

Concrete backer board sometimes has bubbles and voids that aren’t exposed until you cut across them and leave a weak spot or rough crumbly spot at the edge of the piece. You can also damage the edges of the concrete backer board during transport and handling. If this happens, you can repair and reinforce these weak crumbly places with the same thinset mortar that you use to attach the tiles.

Use Thinset Mortar Instead of Glue

Outdoor and wet mosaic should always be done with thinset mortar instead of glue. Thinset mortar is concrete with polymers added for strength and adhesive properties. You can also use the thinset for grouting the finished mosaic. An outdoor mosaic made with thinset will last many times longer than a mosaic made with glue, and that is why they use thinset for attaching tiles in swimming pools.

Using Thinset

We use Versabond brand thinset by Custom Building Products and add 1/4 pound of water per pound of thinset. Thinset comes in big bags that are inconvenient. We keep the bag of thinset in a 5-gallon plastic bucket with a lid. We slide the whole bag into the bucket and cut the top off the bag and scoop out what we need. Never try to pour it unless you like big clouds of dust that is dangerous to breath.

Finding The Right Table Is Easier Than Making The Wrong Table Work

I have always disliked the subject of mosaic tops for metal patio tables because I receive too many emails from lunatics who think the most important thing about the table to be mosaiced is that it is what they already happen to have on hand. It doesn’t matter to them if the table is broken or rusting to pieces or made of wood or already has an expanded metal mesh top welded in place.

For these people, it isn’t about finding a table that is appropriate for a mosaic top, it’s about making whatever they happen to have work, no matter how flawed or problematic or downright dangerous it might be. What’s worse is that when I take valuable time to email back explaining why the table is a poor candidate, they usually email back proposing some farcical method of making it work and wanting further comment.

These proposals show a lack of understanding of basic concepts, but what really makes them insufferable is that they are usually posed as questions asking me to explain why it would not work or why it wouldn’t make the process quicker or easier, usually in a pleading way. (As if my agreeing with them could somehow alter laws of physics or other aspects of objective reality… )

Reading their emails always brings to mind an expression used in the military, one that is blunt, crude and profoundly apt, like so many military expressions: You cannot polish a turd. How many times have I longed to type those words into an email reply!

Inspect Table For Strength And Stability

A mosaic table top can weigh significantly more than the glass top it is replacing. Before doing anything else, inspect the table to make sure it can hold the weight. Look for broken welds in particular, but also keep an eye out for the gauge of materials used for the table. Most metal patio tables are much heavier and stronger than they need to be, but factories make things lighter, cheaper and more disposable each year. If the table in question appears to be light-gauge and weaker than most wrought iron you have seen, then think twice before using it as the base for a mosaic table top.

Bistro Tables

If you use a small metal bistro table, then make sure that you don’t create a safety problem by putting a very heavy top on a table that is taller than it is wide. This can make the table unstable and easy to tip over. The heavy table top could easily injure someone if the table were knocked over by a casual bump. The solution is to anchor or weight the feet of the table, and a sock filled with sand and tied in a knot is often all that is required. Using wire to twist tie the table to the railing of a balcony is another quick solution.

Glass Mosaic Tile Is Best For Outdoors

Glass in nonporous and therefore impervious to moisture and freeze damage. Ceramic tile and stone are porous, and thus water can penetrate inside and freeze and crack the tile over time, sometimes very rapidly depending on where you live. Sure we have a lot of Roman stone mosaics from 2000 years ago, but those mosaics are in the dry warm Mediterranean basin and not west Michigan…

Remember To Seal Outdoor Mosaics

A few days after grouting, you should seal your mosaic with a tile and grout sealer. Tile and grout sealers are invisible pore sealers and not coatings that form a separate layer over the top of the mosaic. You wipe them on with a rag, and then wipe away the excess with a clean rag and allow to dry for ten minutes. Apply it 3 times or whatever the manufacturer instructions recommend.