Artist Jill Gatwood uses the following method to make water-resistant foam-core mosaic backers for exterior mosaics, such as the Pet Memorial Name Plaques she does for clients who need something that is lighter weight and easier to ship than stone or solid concrete. The method wraps the foam in three or four successive layers of fiberglass mesh and thinset mortar, and that coating is pretty tough, tougher than stone. (The combination of polymer-modified cement and fiberglass can withstand blows that would easily crack granite of the same thickness.) Continue reading
Jill’s instructions have convinced me that there are enough mosaic applications for silicone adhesive that we should sell it. Note that we still recommend thinset mortar or Weldbond for mosaics on architectural surfaces such as backsplashes, but for projects such as mosaic mailboxes or glass-on-glass mosaics, silicone adhesive is preferred.
Jill’s steel mailbox instructions are fairly complete and include recommendations for purchasing the right type of mailbox for the project and modifying it as needed.
Steel Mailbox Instructions
1. Selecting The Mailbox
Jill says that a steel mailbox from the big box home improvement stores or a hardware store will work but you have to check it and make sure the metal is strong and doesn’t flex. (In practical terms, this means you should buy the mid-grade or premium model and not the one made for the bottom of the market.)
Jill recommends getting one that has ribs to strengthen the frame if you need an XL size mailbox. Continue reading
I have often used a small screwdriver to pry up tiles when I wanted to change some detail in a mosaic, but in all of those cases, the mosaic had a grout gap, and it was possible to knock an individual tile out or shatter it without damaging its neighbors, at least most of the time.
But what if you can’t afford to damage surrounding tiles or you have a mosaic with no grout gap? Is it even possible to get tiles up? The answer is yes, and the method involves a wet cotton swab, a dental pick, and a sharpened chopstick.
Many people report having trouble cutting vitreous glass mosaic tile reliably because of the embossed patterns on the back sides, which can interfere with the blades of the mosaic glass cutter, but if you take simple steps to minimize interference and rotation, it can be done.
What I mean by interference is when the blade slips down into a valley between two ridges instead of staying positioned in the desired line of the cut. Continue reading
If you work with stained glass over time you can end up with buckets full of scrap. When the pieces start getting too small and irregular, or if there’s just too much of it, you can used them in a stepping stone. This tutorial demonstrates how to make a stepping stone with an abstract pattern. You can also use tiles instead of stained glass scraps.
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.
For dry indoor mosaics, areas can be built up to support thinner tile next to thicker tile by mixing sand or sawdust to Weldbond adhesive to create a heavy paste. You can also fill holes in mosaic backers using this method. Sand is best for minimizing the contraction that happens as the glue dries, but sawdust can be used when weight is an issue.
For outdoor and wet mosaics, thinset mortar can be mixed with clean pea gravel to make a concrete. The pea gravel must be washed clean and dried to avoid contaminating the mortar, and we recommend screening the pea gravel and using only small pieces. Note that you cannot use sand because too much sand will overwhelm the mortar and make it crumbly.
Case Study: Stained Glass Mosaic Coffee Table
Recently our customer Holly LaBarre emailed us asking how to build up areas between wooden slats of a mosaic coffee table she was making. The design concept for the coffee table was to make it look like it was made from pallet wood or wooden planks and put stained glass mosaic between the planks. The problem was that the planks are significantly thicker than the stained glass, but Holly wanted the stained glass to flush with the planks so that the coffee table had a flat surface.
The solution was to put a piece of 1/2-inch plywood on the underside of the table top and then build up the area to be mosaiced using a paste of Weldbond and sand.
The catch is how to build up the area to the right height so that when the stained glass is applied, it isn’t too high or low. To figure this out, Holly made a simple gauge from a straight edged piece of wood that rests on the surrounding planks and has a small piece of stained glass glued to its bottom edge.
Choosing a grout color is more of a situation where you want to avoid making a mistake that causes the tile to look wrong than it is an opportunity to tie in the room’s color scheme by selecting some optimal color.
A Case Study
Recently a customer emailed us the photo above and asked for advice on how to match the grout color to the room’s color scheme, which includes rich gunstock brown cabinets and paint that is pale green or taupe and a black counter top. The mosaic backsplash itself is made from long gray and black tile in varying lengths.
Choosing By A Process of Elimination
Grout colors should always contrast tile colors enough so that each tile is visually distinct. If you were to use a gray grout on this mosaic, the gray tiles wouldn’t stand out as individual tiles. If you used black grout, you would would have the same problem with the black tiles. Since the mosaic is a gray and black color element, a white grout of some shade makes sense. A pure white grout is likely to be too bright, and so an off-white grout that is more or less the same color as the exposed backer between the tiles would be a safe choice.
Too Clever for Your Own Good?
What if you still thought that you needed to tie in the grout color to the room’s color scheme? Then you might consider using some sort of terracotta or brown grout in either a light or dark shade. The problem with that approach is that there are many different hues of gray, and not all of these will look good with a particular brown, even if that brown is optimal for the room.
If you are bent on using some sort of brown or other color for a black-white-gray backsplash such as this, then make sure you take some of the tile with you to the building material store and actually hold the tile up to the grout swatch. That way you can see if the hues look odd together. Avoiding that mistake is much more important than trying to match the other colors in the room.
How You Know This Is Good Advice
Notice how the counter top is black, and the stove and microwave oven are black and silver in color. They don’t have any brown or taupe color elements, but they are perfectly at home in the room’s color scheme. Similarly, the mosaic backspash is a black-white-gray color element that needs nothing extra to tie it in.
Artist Sondra Jonson recently completed a mosaic baptismal font for St. James Catholic Church using our gold glass mosaic and metallic glass tile and vitreous glass tile, and it turned out really well. Religious architecture is supposed to be instructive and inspiring, and so Sondra used a spiral galaxy motif for the bottom of the font and a night sky with stars for the insides of the walls to convey the cosmic significance of the sacrament of baptism.
Laying Up The Mosaic Design
Sondra laid up the mosaic design using mosaic mounting tape, which is recommended instead of fiberglass mesh for outdoor and wet mosaics because glue is used to attach tile to mesh, and glue is vulnerable to moisture. If you use mosaic mounting tape to pick your design up by the faces of the tiles, then you can press the tile directly into the thinset mortar. If you would like to know more, I wrote some instructions for laying up mosaic designs on contact paper and then picking it up with mosaic mounting tape.
Whether you use mesh or mounting tape, you need to minimize the amount of bending and flexing because that can make tiles pop off the sheets. You can use cardboard or plywood panels to lift and transport the sheets. Note that Sondra’s sheets aren’t square for the simple reason that radial sections made more sense than squares because the area to be covered was hexagonal.
Write Down The Names Of Your Tiles!
We recommend that artists save their invoice and glue a small piece of tile next to each product listed on the invoice. That way, you know what you used and where you bought it and when. The date of purchase is as important as the color name and supplier because tile varies by batch, and manufacturers revise their products all the time. Sondra wisely made a sample board for the materials used in the baptismal font in case it ever needs to be repaired or a future client wants to use some of the same materials,
I cannot imagine installing a large public art project without documenting what materials and sources you used. Even if a product is discontinued or revised, which does happen, you or your client will still have the name and the brand and samples for a photo if you make a board like this on for the project. That is a better starting point for finding a replacement from a different supplier than blurry detail shots cropped from photos of the project, which is what people email us all too often.
This mosaic was installed using thinset mortar, which is recommended for all mosaics in pools and fountains and other wet locations. I wrote some instructions for using thinset mortar for detailed mosaic artwork if you need to know more for your project.
The Artist Surveys Work In Progress
Grout does not shrink, but it is prone to forming voids and bubbles if it is not rubbed thoroughly into the grout gaps. These holes are easily repaired.
My friend Fredrik reported a problem while grouting his mosaic portraits of famous rock icons. He described the grout as having shrank in the grout gap.
Real Grout Doesn’t Shrink
The grout didn’t actually shrink, which isn’t possible with traditional grout made from portland cement, sand, and water. (I can’t speak for the newer epoxy-based grouts because we haven’t used them.) What actually happened was that voids were left in the intersections of the groutlines, and these voids got covered with a thin film of grout that then dried out without curing.
Press Grout DOWN Into The Gaps
When you grout a mosaic, it is important to press the grout down between the tiles, and to rub and press the grout thoroughly. Otherwise, voids and bubbles will be left down in the gaps and get covered over with a superficial layer grout similar to how a thin layer of wind-driven snow and ice will sometimes form over a crevasse in a glacier. That is why pressing down is important, and you shouldn’t just rub tangentially across the surface.
You can also “pull” voids into grout by rubbing it repeatedly in the same direction. That is why it is best to rub in circles and to vary the direction of the rubbing randomly.
Avoid Dry Air: Use Humidifiers
Fredrik reported that he wasn’t able to able to spend very long pressing the grout into the gaps because it started to harden almost immediately. It takes grout a while to harden, and this hardening happens by binding water not by drying out, but grout can become prematurely stiff and difficult to manipulate if it starts drying out. Since Fredrik was working in Sweden in February, I suspect the air was very dry due to the heat running, not to mention the already low humidity of the winter air. You can avoid this problem by running a humidifier near your mosaic and by doing the grouting away from heater vents. You can also cover the grouted mosaic with plastic kitchen wrap such as the Saranwrap brand.
How To Fix Holes In A Groutline
The good news is that it is possible to grout voids and holes and bubbles in a mosaic that is already grouted. The only caveat is that the old grout can suck the moisture out of the new grout before it can properly cure and harden. To prevent this, mist the mosaic thoroughly with water before you begin so that the old grout is saturated with water. Note that the mosaic should not be coated with water because droplets of water or a thin layer of water could interfere with intimate bonding. It really helps to have a humidifier running near the mosaic, and you should start the humidifier an hour or so before you grout so that the old grout isn’t bone dry.
Before you regrout, you need to expose all the hidden voids and bubbles. You can do this by pressing on the grout with a small screwdriver and vacuuming out all the loose crumbles. Of course, you need to do this in places that look like there is a problem, and but you also need to press in places that look deceptively fine. You don’t want to have to grout a third time.
I prefer to press straight down instead of dragging the screwdriver because I want to avoid scratching up grout that is fine. If you do get some scratched up grout from your probing, use a stiff bristle brush and a little water on the finished mosaic to buff out the scratches and make them less noticeable.
If you notice that your grout is crumbly in general, you should scrape it all out and regrout. In that case, you might want to use the grout removal tool.
Mixing Up Small Amounts of Grout
One objection to fixing small grout problems is that people don’t want to mix up a whole container of grout and end up wasting almost all of it. The good news is that you don’t have to waste any or at least very much, and you don’t have to be paranoid about whether or not you are adding the right amount of water. You can easily mix up a small amount using a few rules of thumb:
- If you have a small postal or kitchen scale, use 1 part water by weight to every 4 parts dry grout.
- If you don’t have a small scale, add a little water and mix thoroughly. Stop adding water when the grout has the consistency of dough.
- Once you have enough water in the grout, mix it thoroughly to ensure even consistency with no tiny lumps of dry material. These can sabotage the grout hardening process.