Figurative mosaic art (mosaic pictures) can be used as an element of interior design in the same way that paintings are used. The only difference is that a stronger, more secure way of mounting the artwork to the wall is needed.
Natalija wrote an article about using a French cleat mounting system to securely hang a mosaic if you need more information about how to do that, and I discuss some concerns about using picture wire toward the end of this article, but first I want to talk about aesthetic considerations and how to make sure a mosaic looks right in a room.
Small mosaic plaques can be mounted on a wall with a the same type of hangers and wires used for paintings provided the nail on which it hangs is mounted in a stud inside the wall, and even then redundant wires and fasteners are recommended. However, larger mosaics need more robust mounting hardware. The “french cleat” is a type of wall mounting that can be used to securely affix heavy mirrors, cabinets or artwork to a wall. In addition to its strength, the french cleat also allows mosaic art to be mounted flush against the wall and makes leveling it easy.
If you built a frame on the back of your mosaic as described in this tutorial, then french cleat molding is a good hanging option.
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.Indoors
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.Outdoors
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.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.WARNING AND DISCLAIMER
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.
An architectural mosaic can cut someone if sharp edges are left exposed or crush someone if it’s not mounted securely. Even a small mosaic plaque is significantly heavier than a painting or photograph of the same size and should not be hung with light gauge wire or fasteners.Preventing Cuts Would You Glue Razor Blades To Your Shower Wall?
Tighter (smaller) grout gaps helps reduce the potential for cuts. It’s intrinsically more difficult to cut yourself the closer the pieces are together because the closer they are, they less flesh that can be pressed between them.
However, there must be a grout gap large enough to get some grout into during the process of rubbing the wet grout into the cracks. Grout (and thus a gap big enough to be able to press wet concrete into) is needed to seal out water. That is one of the big ironies of mosaic: You can make your mosaic significantly more vulnerable to water damage by mounting the tiles so closely that they touch. Wet concrete might find it difficult to fit into a hairline crack, but water won’t have any problem.Grout Cannot Hide SIns (Forever)
Grout erodes over time, particularly in locations with lots of water and traffic, such as the bathroom floor and shower stall. When the grout erodes, it re-exposes the sharp edges. Don’t use grout to hide safety problems.Repair Damaged Mosaics
Repair damaged mosaics by prying off broken tiles or smoothing with a marble file.Mount Mosaics Securely
The most secure mounting for a mosaic mural is a stone, concrete or masonry wall. However it is possible to mount a mosaic mural on a wood-framed wall provided you review the wall with a carpenter to make sure it’s structure can support the weight.
Smaller mosaics may be mounted using multistranded stainless-steel picture wire with construction-sized wood screws, but install a redundant wire as a back up. Use multiple fasteners in the wood and stagger their locations so as not to split the wood.
Larger murals should use steel mounting clamps or mounting trays. The fasteners should be of structural size and not finishing or cabinet nails. Put fasteners in studs and review your mounting scheme with your carpenter when you review the wall with them. Weights of large murals can be calculated from area multiplied by unit weight, which can be summed from component materials if not actually weighed on a scale.
Make sure you have a carpenter look at the wall to see if it can bear the load.
Frames That Match The Art
If the mosaic is a mixed-media mosaic with rounded and irregular sculptural elements, a frame in the style of a generic photo frame or document frame may look out of place with its uniformity and minimalism and linear perfection.The Merits Of Reclaimed Wood
I think reclaimed wood with some naturally worn edges and grooves works very well, especially if you use the surface of the wood without sanding off all the wear and join the wood in such a way that matches the worn character of the wood. Reclaimed wood is a great example of downcycling in art and using repurposed materials.
Wood bleached white from the sun might not be as useful as indoor wood that was been aged to a warm color.
I salvage solid wood desks and chest-o-drawers when I see them on the side of the road, but here I’m talking about larger pieces salvaged from a house, maybe something roughly 1.5 to 2 inches thick, maybe something from an oaken door frame.
Original nails can be good, preferably square, preferably flush with the surface or near to flush. Rust stains, knots, old peg holes, notches, channels and dovetailing are good features to look for when choosing your wood.Joining The Corners
I wouldn’t cut the wood to make a 45-degree mitre joint like a manufactured frame. The joint should not be a super-straight line with crisp corners if that isn’t how the other edges of the wood are.
How I attach the pieces together at the corner joints depends on the sizes, shapes and end details of the wood I found.
I like to notch things like the logs at the corners of the log cabin. In a cabin, the logs are notched shallow enough so that a log sits slightly above the two logs it is sitting on. For a mosaic frame, I cut deep notches so the four sides are all a the same level in the same plain and not two sides higher than the other two.
No Daniel Boone, you don’t use an axe to notch something this small. Instead, use a wood chisel and mallet. You can cut a notch by making repeated passes on a tablesaw set to shallow depth, but I don’t like how uniform and crisp the tablesaw is compared to the wood chisel.
You can peg the notch-joint corners with a rusty square-cut nail or brass wood screw from the front or a more generic fastener hidden from the back based on preference.
A shallow pan of a dilute bleach solution can accelerate rusting of steel nails and other findings.Finishing Cuts
The edges of any cuts need to look like the rest the wood. Round the edges of cuts by light controlled blows with a hammer and burnishing with an old rag that gives off traces of shoe polish or wood stain, not sanding. Better yet, look for pieces of wood that are slightly longer than needed and extend out to the sides.
If a piece of old wood is too wide, consider splitting it instead of saw-milling it in a tablesaw.Attaching Frame To Mosaic
The frame should be built around the mosaic. What I mean by that is every time you join a corner, fit it onto the mosaic to test the fit before and after driving the fastener.
I would probably have the surface of the frame be about 1/2 inch to 3/4″ inch above the surface of the mosaic but do it in a way that didn’t cause a problem shading or obscuring details. That is best accomplished by using wood that is thinner or more worn down on its inside edge.
Make sure that your mosaic is securely integrated with the frame and can’t just pop out. For esthetic and structural reasons, the frame needs to be part of the art. Use adhesives and fasteners for safety’s sake. Use your wood chisel to make sure the mosaic fits snugly inside the frame.Mounting The Mosaic
Smaller mosaic plaques can be hung using stainless steel multi-strand picture wire provided the weight isn’t too great and the mosaic is being hung where it cannot be brushed by someone walking past and isn’t hung overhead.
A mosaic is significantly heavier than a painting or photograph. Use double mounting wires. Use stainless steel multi-strand picture wire.
Attach the first wire to nails in the back of the wood, not silly little screw eyes such as sold for hanging pictures. Wrap the wire under the heads of two nails on each side, first one nail, then the other down below it. That is your back up nail on each side.
The second wire is the backup wire, and it runs to the same 4 nails and is wrapped under the nail heads over the top of the ends of the first wire.
The nail should be selected for having a broad head, but don’t use a roofing tack. The heads of roofing tacks tend to break off easier than most nails. A screw with drilled pilot hole is preferable to a nail.
You must not use wood that is too brittle or worn out to be structurally sound. The fastener will pull out or split the wood over time. Use good carpentry skills and stagger the fasteners so that they don’t split the same grain.
The mounting wires need to hang on a fastener of structural size in the studs of the wall.Use Metal Mounting Brackets Not Picture Wire For Large Mosaics
If your mosaic is large and heavy enough, it needs to mounted with metal brackets similar to those used to mount mirrors, not hanging on a picture wire. Mosaic murals of this size may not need a frame.Where To Get Materials
A carpenter friend who renovates old homes throws a lot of amazing art material into dumpsters all the time: oak flooring, oak door frames, old floor joists and ceiling beams. I’ve always been grateful that I’m tall enough to peak over inside a construction dumpster.