Monthly Archives: May 2014

Outdoor Mosaic Signs

In the last section of one of my previous posts, Custom Shapes For Mosaic Backers, I showed some pictures and instructions for how I used 3/4-inch expanded steel to make a backer for an outdoor mosaic. The expanded metal was welded together in 3 plies, some mounting bolts were welded to this, and then the expanded metal was coated in thinset mortar fortified with very small pea gravel to form a solid surface. (Note that the assembly was cleaned with a wire brush to remove oils and dust before the thinset was applied.)

Built To Stop A Tank

I used this method of making a backer with built-in mounting bolts for two reasons: First, I could make the shape irregular and still have very strong edges without a metal border (which could have been welded on before applying the thinset if needed). Second, I wanted the backer itself to be incredibly strong because I wasn’t making a sign. I was making a backer for a found-object mosaic, and I didn’t want there to be any possibility of the backer flexing and cracking artifacts or not being durable. Third, I wanted the mounting bolts to be integrated with the backer itself and not secured by some separate frame which held the backer.

Some Lighter Weight Options

One negative consequence of making something this strong is the resulting weight. However, there are some options to bring down the weight considerably. The first option would be to use a lighter gauge of expanded metal, or maybe only using one ply instead of three plies and then wrapping that in hardware cloth before plastering with thinset. Another option would be to use the Wedi Board product or a concrete backer in a frame made from 3/4-inch angle iron and weld your mounting points to the frame. I don’t think I would use concrete backer board for this latter option because the edges tend to be crumbly. I would probably use light gauge expended metal coated with thinset even if I set this in an external frame.

Backer In An External Frame

If you do go the route of mounting a backer in an external steel frame, there are several things to consider:

First, remember to paint the frame with at least 3 coats of oil-based outdoor paint after all welding is done and cleaned, including all mounting studs and devices needed to lock the backer board into the frame (such as nuts welded onto the frame to accept a small bolt that keeps the backer from slipping out).

Why you need a locking device:  You cannot rely exclusively on an adhesive means of keeping the backer in the frame because the backer could potentially delaminate over time. Depending on the size of your mosaic, you may need to use a heavy gauge of angle iron or nest two pieces for each element of the frame.

Estimate the weight of your finished mosaic and make sure the frame can support it. Make sure the  the corners are double welded and make use of corner braces to help ensure that the bottom of the frame doesn’t pop off if the frame rusted badly over the years.

For added effect, make the frame part of the art and not an afterthought or just a default to a conventional rectangular frame. Consider a frame that grasps a reinforced backer at several key points instead of a more conventional frame that wraps all exposed edges. Of course, that requires a thicker backer, or at least a backer with a hollowed-out back and thicker outer edges.

Mounting Bolts Welded Directly To Backer Skeleton

If you decide to use my approach of creating an expanded steel skeleton covered in thinset mortar with mounting bolts sticking directly out of the concrete, then you need to weld the different plies of expanded steel so that they provide a good place for the head of the bolt to be attached to the central ply of steel.


A nut is used to hold the bolt onto the expanded steel. The nut and bolt head are welded in place. Note that there are several places in this picture where the different plies of expanded steel need to be welded together.

Make sure you use a carpenter’s triangle to make sure your mounting studs are vertical. Sometimes you have to tack weld the bolts in place and then bend the weld slightly to get them straight.

Another concern is the potential for the mounting studs to rust over time. The water running off concrete tends to be slightly alkali and corrosive to steel. I would spray paint the back side of the backer, especially around the mounting studs. You should also consider using larger gauge bolts for your mounting studs.


Mounting stud from the reverse of the backer. Another coat of thinset mortar should be applied to fill the voids and ensure that all of the expanded steel is covered.

Before I began mounting the mosaic tile to the backer, I would make sure that the edges of my backer were finished properly and apply extra thinset to cover any bare expanded steel sticking out so that there aren’t any safety or corrosion issues over time. Of course, this is easiest if you did a proper job of welding and cleaning the edges of the expanded metal so that there aren’t any sharp points to begin with. Make the edges of the metal skeleton as robust as possible with thick globular welds and clean these thoroughly.

Mounting Mosaic Signs

There are some comments at the end of my post about Custom Shapes For Mosaic Backers, that discuss the issues involved in mounting a mosaic sign to a masonry wall.



How To Select A Jigsaw For Making Mosaic Backers

Tools Are Cheaper Than Craft Supplies

I have often made the claim that a person could buy a sheet of cabinet-grade plywood and a jigsaw for less than what the craft suppliers charge for shaped mosaic backers such as hearts and stars and things like that. While this might be an exaggeration for an individual backer, it is perfectly true if you need to get backers for a class of 20 people. In my post about making custom-shaped  mosaic backers , I also explained why it is better to cut your own shapes if you are trying to make original art because you can make each shape slightly different and unique.

Jigsaws are fairly common, so you might be able to borrow one, but here are some guidelines if you decide to buy your own. Note that jigsaws are best at cutting curves. If you need to cut straight precise lines, then you need to use a circular saw or a table saw, but keep in mind that those two types of saws are more dangerous than a jigsaw.

This post is not a review of models currently on the market. Instead, it is discussion of general principles that should help the reader make a more informed purchase for any type of power tool or electronic device.

Never Buy The Cheapest Model

Never buy the cheapest model. In the past, there was a problem with things not lasting very long, but the trend of making things cheaper and cheaper has progressed to the point that it is now possible to buy tools and electronics that don’t work or barely work even from the beginning. Most people can walk into a dollar store and recognize the type of products I am talking about. What you might not be fully aware of is that this problem with non-functioning and barely-functioning products has spread to more mainstream retailers such electronics chains and home improvement chains

Manufacturers know that many buyers are completely uninformed and buy a new product solely on the basis of lowest price. Consequently, they all are “forced” by economic pressures to produce at least one model geared toward the bottom of the market.

Never Buy The Lowest Amperage

The power rating of jigsaw is expressed in terms of the amps of electrical current that it consumes at full speed. Due to the economic pressures expressed above, manufacturers now produce power tools that no informed buyer would ever purchase simply because they aren’t powerful enough for most jobs. These low-amperage tools just don’t have the power to be useful or last very long.

Don’t Buy A Rechargeable Tool

Rechargeable batteries only last if they are depleted fully and recharged fully. Occasional light use and continual charging is bad for the battery and destroys the battery’s ability to hold a charge.

Unless you work as a carpenter and use your tools daily, get a jigsaw with a power cord. The environmental cost of all these rechargeable batteries is simply too high, especially when they are used in ways that more or less guarantee that their life is short.

Don’t Buy Features Over Quality

Everyone is familiar with a certain computer operating system that owes its success to having a lion’s share of the market and to the monopolistic practices of the company that sells it.  Each new version of this operating system offers ever more bells and whistles, while the software itself still suffers from the same basic problems with stability and useability that have plagued it for years. The economic reasons for this situation are simple: New features make the product outsell the competition, even when the “competition” is merely the older version of the product that the consumer might reluctantly continue to use.

To a certain extent, features can become a trap where it is possible to buy the most cheaply made product even when you thought you knew better than that. For example: You may have been smart enough to avoid buying the absolutely cheapest model, but did you buy the cheapest model with the laser guide or some other feature? The question becomes this: How cheaply did they have to make the jigsaw itself in order to include a laser guide and still be the cheapest model with that feature?

Read NEGATIVE Reviews

Always read online reviews, even if you plan to buy locally. is frequently a good source of information for common products, but keep in mind that even a poorly designed product will get some positive reviews. I think this is because some people are just glad to open the box and tell people about the new toy they just got. Often these mindlessly positive reviews will more or less admit as much: “I just received my new JuiceTronic 9000 Smoothy Machine, and I am so excited…”

The key to making use of reviews is to read the negative reviews and find out how long the product tends to last, what design defects it might have, etc. You want to know what the man thinks after he has divorced the princess, not what he thinks on the day he married her.

All that being said, you have to take negative reviews in context. Even the best product in the world is likely to have some negative reviews. Remember that some problems are due to abuse or user error or the odd lemon, and some people are just mean-spirited trolls that are angry at the world.

At one point on Amazon, there was this guy who gave negative reviews for the Sharpie markers because these markers (which are clearly labelled as permanent markers and famous for being so permanent) wouldn’t erase off his dry erase boards. Some people are just ignorant and proud of it.


Long-Term Art-Studio Experiments and the Pace of Mosaic Composition

Don’t Rush The Design Process

It is easier for me to explain what I mean about pace and long term experiments if I discuss my painting instead of my mosaic artwork. Compared to most mediums of visual art, mosaic isn’t typically executed in a rush because the amount of work usually requires multiple sessions in the studio. (You don’t slap on some tile quite as quickly as you do paint.) However,  the point I make about my painting has a lot of relevance to the process of DESIGNING or CONCEIVING a mosaic composition and how you reflect on the work in progress and evaluate color decisions as you go along. Never blindly execute what you initially guessed to be a good decision. The design “mode” should never be turned off if your are trying to make great art.

joe's painting studio

I think the highest form of visual art is finding objects in clouds. This is an aspect of dreaming that occurs while we are awake. I like my paintings to resolve into compositions as I go along with figures emerging from a dance of color and texture.

Artificial Deadlines Are A Double-Edged Sword

Accomplishment builds confidence, but what are you accomplishing if you aren’t happy with the results?

Not long after starting Mosaic Art Supply, I found myself working on painting more than mosaic, at least in the studio time that I set aside for my own projects. (Go figure.) I made the decision to work on my painting in the following way: I would complete a small painting in a single session each night and then write something about creating it (personal significance or techniques) and then publish the painting’s photograph and text online. I didn’t use a blog format, but it was essentially a blog, with pages named for the artwork in question and no dating. Most of my paintings at Riverson Fine Art were created in this way.

This one-painting-each-night approach was great for getting me accustomed to “finishing” work, but the constant artificial deadline of having to be done that night also made me hectically overwork some paintings (because I didn’t spend enough time looking at what I was painting and felt a rush to go with snap decisions). I also didn’t allow enough time to figure out technical questions before the lack of knowledge showed on the canvas in a clear way.

It became clear that this exercise of doing rapid experiments each night could only teach me so much, and it had clearly taught me some bad habits that I had to unlearn somehow.

Kids Don’t Try This At Home

My solution was to totally change the pace of how I created art and not worry about publishing it or showing it. (The mosaic business was giving me more of a public presence than I wanted anyway.) But I did much more than this: I went to the opposite extreme. I didn’t even think about individual compositions or at least completing them as compositions. I drew up long lists of technical questions I needed to answer (such as how to mix up any color, ANY color I might need, shade or hue), and then I laid out what experiments I needed to do to find the answers.

More than that, I allowed myself to digress into a series of smaller investigations if I got stumped on a particular color or problem, no matter how irrelevant the issue seemed by itself. It was merely enough that I couldn’t answer the question, and I worked until I figured it out. I wanted to know how to do whatever it was in the event the same issue ever came up later when I started painting figurative compositions again.

This might seem obsessive on the surface, but I had already painted enough canvasses in a completely unsatisfactory way to know that I wouldn’t have the confidence to complete anything until I was more technically competent.

In the case of how to mix up any shade or hue, I simply painted a series of mixing grids, such as recommended and discussed in most books about how to paint.

To get the type of effects I wanted, I also needed to know how these colors looked when imperfectly layered over a canvas textured with peaks of modeling paste so that the layer underneath showed in the valleys. This greatly multiplied the number of variables I had to figure out.

How would these look when color complements were paired? What about warm on warm or cool on cool? How would they look with dark on light or vice versa? How did making the upper layer more translucent with medium affect the hue of the layer underneath? How did varying the size and type of texture affect ALL of the above?

Should the texture be rounded or sharp? Should texture run in raised ridges at the edges of figures? What would be the most effective way of duplicating specific results I found pleasing? How controlled or random should the sequence of layering be?

And then there was my META question: If I mastered all of these variables, could I use the resulting techniques to make quick-drying acrylic paint look as visually interesting and complex as slow-drying oil paint, which naturally diffused creating soft edges and subtle transitions of hue?

The answer could only be found by executing all of these combinations in a lengthy series of large abstract canvasses that took literally years. Each canvas was painted 10, 20 times, maybe 50 or more. Not 50 layers of paint. I mean 50 uses of the canvas for different “compositions” of multiple layers with all the accumulating texture that provided. Some of my canvasses from this period are almost as heavy as mosaics.

Finally, just 6 months ago, I felt that I had investigated enough unknowns to have a vocabulary of techniques sufficient to attempt a figurative composition again with confidence. So I started painting figurative works again, or rather, I started trying to paint figurative compositions again, and I felt anything but confident.

For starters, it wasn’t that easy to stop digressing each time I had a question about hue, texture or other variables in combination. I had gotten in the mode of “find out how” not “wing it to complete the composition.”

Also, I had to factor in how I developed compositions. I don’t work from a model in front of me. I work from hundreds of remembered models arranged in imaginative compositions. I draw from the imagination. I also work interactively with the canvas to allow figures to evolve from seemingly random strokes. I like to let the design emerge from the canvas in a way similar to how the mind sees objects in clouds, which I think is one of the highest forms of visual art.

All of this is fairly absorbing and cannot be done if I am having to concentrate too much on how to get the effects I want.

The long and the short of it is that I finally have a painting near enough completion to show after years of one long extended series of experiments that took over 4 years.

Color Dance unfinished painting

This painting is unfinished. I am thinking of calling it “Color Dance.”

Parallels with Mosaic Art

In a mosaic, you may not have layering of color as a variable, but you definitely have juxtaposition of color, and you have variegation of color fields and color field transition. You also have how all of these variables are affected by tile size and work lines (andamento: how the tiles are arranged in contours to show motion or  arranged randomly or grid-like). Think about all these variables and how they might be used to make your composition stronger. Of course, you don’t have to go completely mental like I did with painting and try to think about every combination of variables, but do spend some time thinking about what else might be before you begin setting tile in concrete.

A Practical Way To Experiment In Mosaic

Draw a cartoon (outline) of your design on the mosaic backer with a pencil, and then just place tile in the different color fields. At first, think about just different pairs of complementary colors, and try to get the basic color layout planned. Then think about how each color field might be made more visually complex by adding a few related hues or shades to the color field instead of using only one hue or shade. Once that is fairly worked out, then think about what size the tiles should be and how they should be arranged. It is hard to go wrong by arranging tiles in lines parallel to the outlines of figures. These contoured work line suggest motion, and this almost always looks more interesting than random patterns or grids. Remember, you aren’t tiling a shower or bricking a wall. You are rendering an image, so take advantage of all the trompe l’oeil you can, especially andamento!

The meta message is this: You can’t tile over an unsuccessful part of a mosaic the same way you can quickly paint over an unsuccessful part of a painting. This means that designs are enhanced when you do quick experiments with your cartoon BEFORE you start mounting tile: merely lay the tile out loosely on your outline and see how the colors work together. Try different combinations. You can’t try them after the tile is glued down, or at least as easily. Make haste slowly and avoid the need to chisel off glass tile.

Advanced Tips For Selecting A Grout Color

The primary reason for grouting tiled surfaces is to prevent water from penetrating behind the tile and weakening the adhesive or the backer and the structure beneath the backer. In mosaic artwork, the grout also has a visual function, and that is to contrast (not match) the tile colors. If the grout color does not sufficiently contrast the tile colors, than all the tiles blend together visually, and much of the “mosaic effect” is lost.

Grout Color Should Contrast Not Match

There are some novices who doubt my advice about contrasting grout color and even try to match their grout color to the tile colors. These are the people who later email me in a complete panic. They usually use the words “completely ruined” to describe what grouting did to their once beautiful mosaic, and from the pictures they send, I’m inclined to agree with them. (Note that these mosaics can be saved, but it requires either scraping the grout out with a grout removal tool or painting the grout with acrylic paint or some other ad hoc solution.)

A Medium Gray Grout

Since experience has shown time and again that the best grout color is one that contrasts tile color, the question becomes which grout color best contrasts ALL the different colors used in the mosaic. For MOST combinations of tile colors, the best contrast is usually provided by a medium to dark gray, with darker being the better guess if in doubt. Always keep in mind that the color of the grout will be significantly lighter when fully cured compared to how it looks when wet.

A Notable Exception: Lighter Blues

There are a few notable exceptions to the rule of gray grout being best. The most obvious exception is when you are using gray tile (duh), but the one that usually catches people by surprise is when tiles of lighter blue colors are used. Unfortunately, these are just the shades of blue that are popular for water and sky elements, so this is a significant exception. In this situation, a warm light brown or sand colored grout might be a good choice for contrasting the blue tile, but what if there are light brown tile used elsewhere in the mosaic? Is there a good standby color of grout for this situation? The answer is no, but there is a quick solution.

Go Look At Grout Colors With Your Tile

Building material stores such as Home Depot and Lowes usually carry about 30 or more colors of grout, and they have color swatches on the shelves and/or packaging so that you can pick out grout similar to how you pick out paint, only with much more limited options. The trick or tip is to not to try to do this from memory without the benefit of having your tile with you. Take one or two tile of each color used in the mosaic with you to the store and hold them up against the color swatches. I have even gone into the store with small mosaics, just as I have taken in parts of plumbing I was trying to match or replace. Don’t be self conscious about it. The people who work there are accustomed to seeing professionals at work, and you will be quite unobtrusive compared to the building contractors dealing with emergencies. At least you won’t be covered in dirt and holding a toilet seat or something like that.

Some “Advanced” Tips

From the many emails and pictures I have received in the past 12+ years, I can state with some confidence that novices tend to regret choosing grout colors as an attempt to add another color to the mosaic. Matching grout color to tile color tends to be even more disastrous.

If you already have your figures rendered in tile using a relatively small grout gap, and you like how those figures look, then your main objective while grouting should be to not mess up the visual art that was already working, especially if you are a novice at mosaic.

Of course, even a novice can take a few of each color tile and create an abstract experiment on a scrap piece of plywood and try a novel grout color on it.

The monochromatic nature of medium gray grout makes it contrast colors intrinsically, in the same way that back and white contrast colors intrinsically. All three are balanced in hue. The keep-it-simple and less-is-more principles really come into play when you decide to second guess some shade of medium to dark gray when grouting figurative mosaic artwork.

On the other hand, there are all those earth tones to play with…

Just remember to experiment on a piece of scrap before trying it out on a mosaic where 90% of the work was spent cutting and mounting the tile.

How To Make Custom Shapes For Mosaic Backers

Rectangular backers are fine for most mosaic designs, but sometimes you want to make an irregularly-shaped mosaic or a mosaic with a custom shape, such as the silhouette of a common object: tree, automobile, flower, turtle, etc. How you make such a backer and what materials you use depends on whether or not the mosaic will be installed in an outdoor or wet location. Note that not every location in a kitchen or bathroom has to be considered as being “wet.”

First, I will discuss irregularly-shaped backers, and then I will explain how to make custom-shaped backers for both indoors and outdoors. The last section about custom-shaped backers for outdoors should be useful for people making mosaic signs and placards.

Why You Should Not Buy A Shaped Backer

If you buy a shaped backer from a craft supplier, then your mosaic will have exactly the same shape and size as all the other mosaics made from that particular backer. Also, most of that craft crapola is designed in China, and it all looks rather dated. The saddest customer picture we ever received was a picture of a beautiful mosaic design (serious, intense, original) executed on the most boring, cutesy, cliche shape of a ladybug. Oh what might have been…

Irregularly-Shaped Backers

If you want more of a random “found” shape instead of a specific shape, then the solution is to use a piece of scrap plywood or flagstone depending on whether or not the mosaic is outdoors.


For indoor mosaics, you can use a piece of 1/2″ cabinet-grade plywood, and a local carpenter or cabinet maker can give you more than you could ever use. Check with friends and their spouses for a few pieces of scrap, or you can buy a sheet of cabinet-grade plywood at a building material store such as Home Depot or Lowes and have a friend cut out what you need with a jigsaw. You can also buy a decent jigsaw for about $75, but make sure you follow the safety instructions and maybe watch a safety video or two on Youtube if you are a novice with power tools.


For outdoor mosaics, you should not use wood or adhesive. Wood doesn’t even have to get wet for the humidity in the air to swell and warp it. Instead of the glue-then-grout method used for indoor mosaics, you should use thinset mortar to attach the tiles to a stone or masonry surface. Concrete backer board can be used for rectangular and circular mosaics that have some sort of frame (such as the rim of a metal patio table), but the edges of concrete backer board can be crumbly, and that makes it a lot less useful for irregularly-shaped mosaics where the edges are left unfinished, such as you see in the fragments of ancient Roman mosaics displayed in museums.

To make an irregularly-shaped outdoor mosaic in the style of a Roman or Greek fragment, use a piece of flat flagstone such as can be found at stone stores, landscaping stores and some higher-end lawn and garden centers. Avoid slate and sandstone, especially the softer varieties. You can get a general idea of how soft or brittle a type of stone is merely by paying attention to how it has been breaking or scratching or weathering in the big piles or stacks at the stone store. Slate is good and flat and smooth, but it tends to be thin and break too easily for most sane people to care about mosaicing on it.

Custom-Shaped Backers For Indoor Mosaics

For indoor mosaics, 1/2-inch cabinet-grade plywood is my preferred backer, and it is sold at most building material stores. It comes pre-sanded and is more resistant to warping than the cheaper plywood used for construction sheathing. There also fewer if any internal voids in the plies of wood, so the edges are stronger and look neater. The few extra dollars for cabinet-grade plywood are worth the cost.

The shape of your backer can be drawn directly on the plywood with a pencil, or you can first draw the shape on cardboard or paper and then cut it out and use it as a stencil and trace the shape on the plywood.

Cutting the shape out is best done with a jigsaw, which can be bought for about $75, but you can ask friends and their spouses to do it for you if they have one. Most people who work with carpentry or cabinetry will have one, but if you decide to cut it yourself, make sure you watch an online safety video about using jigsaws first. In my opinion, jigsaws aren’t nearly as dangerous as circular saws and table saws, but novices should be extra careful when using power tools.

 Custom-Shaped Backers For Outdoor Mosaics

Metal isn’t recommended as a mosaic backer, but if you are mounting the mosaic outside, then metal will probably be involved in some way, at least in how the mosaic is attached to the building or post. The most obvious solution is to have concrete backer board set in a metal frame made from angle iron, and this frame can have mounting studs (bolts) welded to it prior to painting it and inserting the backer board.

I don’t recommend hanging mosaic signs from chains because mosaic work is heavy, and intense wind from storms can turn the sign into a battering ram. Also, the chains would need to be checked periodically for wear, and the artist cannot guarantee that the owner of the sign will do this over time.

Of course, a frame made from angle iron is really only practical for rectangular shapes.

My approach for making a custom-shaped mosaic for outdoors was to put the steel inside the concrete. Essentially, all I did was cut out my shape in 3/4″ expanded steel using a cardboard pattern as template, then weld mounting studs (bolts) to it, and then I encased it in thinset mortar, which is a type of sticky concrete.


Expanded steel 3/4 inch. The 3/4 inch measurement refers to the size of the internal holes, specifically the minor axis (shorter dimension) instead of the longer side-to-side dimension.

The 3/4″ expanded steel was cut using an angle grinder with a thin cutting wheel because I didn’t have a cutting torch and haven’t yet saved up enough money to buy a plasma cutter. (Are you listening Santa?)

I used my cardboard template to outline two pieces of expanded steel, and I made sure that the direction of the expanded metal was oriented at 90 degrees between the two pieces. That way when I welded them together, I was sure that the holes would not line up perfectly. Instead, I wanted the holes in each piece of metal to be partially covered by the other sheet.

welded expanded metal

This structure was made from scraps of expanded metal I had in the shop instead of two pieces expressly cut out for the job, but notice how I made sure the expanded pattern in the top and bottom layer are still rotated 60 degrees from each other instead of perfectly lined up. A rotation of 90 degrees is optimal for ensuring the holes in the resulting structure aren’t too large.

Once I had my shape welded together, I welded some 3/8-inch bolts to it to that the finished mosaic could be bolted to a wall. Then the frame was scoured with the stiff wire brushes that are used to clean welds.

The thinset mortar I used to cover the frame was applied in multiple coats. The first coat was mixed with about 50% fine pea gravel so that the mortar had some bulk to fill the holes in the frame. Note that most pea gravel you see at lawn and garden centers will need to be sieved through 1/4″ hardware cloth or at least have the larger stones picked out. If that seems tedious, then consider how tedious it will be to pick put the large stones once they are coated in sticky concrete but are too big to be pressed into the frame. (Been there.)


This is the underside of a finished outdoor mosaic backer. Note the three mounting studs. Also note that the top surface (facing down) is a lot smoother than this backside. I made the top surface perfectly smooth by applying a second coating of thinset to the top face and then setting it upside down on a piece of construction plastic.

Thinset mortar contracts or “thins” as it cures, so there isn’t much point in making your surface perfectly smooth with the first application. Of course you want it level, and you don’t want any large pieces sticking up, but there is no need to try to smooth it to a finished surface with a trowel. If you do smooth it perfectly, you will notice dimples that get larger each day for about a week as the thinset contracts internally.

Due to this internal contraction and the resulting dimples, I wait about a week before applying this second coat, which mainly involves spreading the thinset on the face with a putty knife or trowel and then turning the mosaic face down on a piece of construction plastic.


Roll of construction plastic. Grout does not stick to plastics in general, but this stuff is especially good about being stick free.

Construction plastic is sold in large rolls at building material stores. A cheaper alternative is clingy kitchen wrap such as the Saran Wrap brand. Kitchen wraps aren’t as strong, and they don’t tend to stay put even when taped down, but an easy solution to this problem is to find a large piece of cardboard and wrap it around the cardboard about 3+ layers deep. Then you can lay the covered cardboard on your work surface.


Use this improvised method and these instructions at your own risk. Like all the instructions on my websites, these instructions haven’t been rigorously tested in corporate laboratories. Neither can they anticipate all the potential mistakes an individual could make in executing them. As always, if you are installing anything for a client, it is your obligation to evaluate the strength, safety and longevity of your art, especially if it is to be displayed in a public space.

All that being said, there isn’t too much if anything in these methods that uses materials in a way that they aren’t commonly used or at least in a similar way. Unless you weld things in an amateurish way or fail to clean the welds, then the backer should have a very long life, even outdoors. The only mode of failure I am particularly concerned about is the possibility of the bolts rusting through over time, although that would be a concern with any heavy sign mounted by bolts.