By Juanita Canzoneri

One of the best ways to save money in your mosaic art process is to look at things differently.

Instead of buying an expensive shaped base, can you use something you already have?

Sometimes the answer is yes.

But sometimes a free or inexpensive object isn't really a bargain. (To quote Judge Marilyn Millian, “the cheap comes out expensive”.)

When you're choosing a base for a mosaic, you need to think about more than whether you can glue a piece of tile to it. You need to think about what that material will do over time.

Two materials that can cause problems are drywall and plastic.

Let's take a look at why.

Drywall: What's Inside?

Drywall might seem like a great material for a mosaic base.

It's inexpensive, easy to cut, and readily available. You may even have it already on the wall you want to work on or have leftover pieces from a remodeling project.

But drywall wasn't designed to be a structural base for a mosaic.

The material inside standard drywall is primarily gypsum, a mineral-based material made from calcium sulfate dihydrate. The gypsum core is sandwiched between layers of paper.

And that paper is one of the first things that should make you stop and think.

The Paper Is Part of the Problem

The outer surface of drywall is paper. Even covered with a layer of paint, it’s still paper.

That paper gives the drywall its smooth surface and helps hold the gypsum core together, but it is not a good foundation for a mosaic.

Think about what happens when you add your mosaic materials.

You would be adding glass or ceramic tile, adhesive, and grout.

That's a lot of weight being supported by a material that wasn't designed for this purpose.

When you're using a water-based adhesive or grout, moisture will affect the paper surface. Wet paper is not strong enough to hold onto these. Failure is really its only option. And there goes all your work.

Gypsum Can Absorb Moisture

The gypsum core itself is porous as well.

That means it will interact with moisture from materials you're using to attach your mosaic.

If you’ve ever seen wet drywall, it’s not a mess you want to invest time and materials into.

Instead of giving you a stable, predictable surface to work with, you're asking a wall-building material to perform a job it wasn't designed to do.

And even if everything appears fine when you finish your mosaic, the real question is:

How will it perform six months or five years from now?

So How Should You Plan to Create a Backsplash?

Rather than planning to mosaic directly onto your wall, use a reliable substrate. I’ve worked backsplashes onto 1/4” hardboard cut to fit the space you’re working into. Primed with water-based wood primer of course.

Create your design on this. Once your mosaic is affixed to the board, put this into your backsplash space and fix it to the wall by screwing into the studs. Then grout.

What About Plastic?

Plastic is a little trickier because "plastic" isn't one material.

There are many different types of plastic, and they don't all behave the same way.

That's important when you're looking at found objects.

You might find a plastic container, bucket, tray, toy, mailbox, garden object, or some other interesting shape and think:

"This would make a great mosaic!"

Maybe it would.

But first, you need to figure out what you're actually working with.

The Adhesive Problem

One of the biggest challenges with plastic is getting your adhesive to bond reliably to the surface.

Some plastics are notoriously difficult to bond to.

You can rough up the surface, clean it, use a primer, or choose an adhesive specifically formulated for a particular type of plastic.

But the fact that you can get something to stick initially doesn't necessarily mean you've created a permanent bond.

That's an important distinction.

Your mosaic might look perfectly secure when you finish it.

The question is whether the bond will still be secure after the piece has been exposed to temperature changes, moisture, sunlight, and normal use.

And how will the grout react to these changes?

Plastic Can Be Too Flexible

Another problem is movement.

Some plastic objects are flexible.

That may not seem like a big deal until you cover the surface with tile and grout.

Mosaic tile and grout don't react well to being bent back and forth.

If the base flexes every time the temperature changes, you sit on it, pick it up, or even press against it, the mosaic attached to the surface has to move with it.

Eventually, that movement can lead to:

·         cracked grout

·         loose tiles

·         broken adhesive bonds

·         or sections of the mosaic coming away from the base

I learned this lesson from a mosaic made on a plastic mailbox.

Debbi mosaicked her mailbox and it looked great, for a while. But the plastic had enough flexibility that it could move after the mosaic was finished.

That movement eventually became a problem. After a while all of the grout was gone. This exposed the adhesive which, while it lasted longer than the grout, eventually began to fail too.

Sometimes you have to learn these things the hard way.

Heat and Cold Can Matter, Too

Think about where your plastic object will live.

A plastic object sitting in direct sunlight can get surprisingly hot.

Then it cools down at night.

Outdoor temperatures can change dramatically from one day to the next, and the material can expand and contract as its temperature changes.

Different materials expand and contract at different rates.

Your plastic base may move one way while your tile, grout, and adhesive move another way.

Repeated movement can put stress on the mosaic.

This becomes especially important for outdoor projects.

UV Exposure Can Damage Some Plastics

Sunlight is another consideration.

Ultraviolet radiation can cause some types of plastic to become brittle, discolor, weaken, or otherwise deteriorate over time.

You may start with a strong-looking plastic object and end up with something very different after years of exposure to sunlight.

If your mosaic is intended to be outdoors permanently, you need to consider how the base itself will hold up—not just whether the tile is rated for outdoor use.

Is All Plastic Off-Limits?

No.

This is where things get a little more complicated.

There are many different plastics, and some can be perfectly useful for particular mosaic applications when the right adhesive and preparation are used.

The point isn't that every piece of plastic is bad.

The point is that you shouldn't assume a plastic object is a good mosaic base simply because it is sturdy enough for its original purpose.

Before you use it, consider:

What type of plastic is it?

How flexible is it?

Can your adhesive bond to it reliably?

Will it be exposed to sunlight?

Will it get wet?

Will it experience large temperature changes?

Will the object continue to flex or move after the mosaic is finished?

If you don't know the answers, that inexpensive found object may not be the bargain you thought it was.

What about Resin?

Here's one exception worth mentioning.

You may come across statues and decorative objects described as "resin."

Resin objects aren't necessarily the same thing as flexible plastic objects.

A solid, rigid resin statue can sometimes make a perfectly reasonable mosaic base, provided the particular material is suitable and the surface is properly prepared for the adhesive you're using.

Again, don't assume that every object labeled "resin" is the same.

Look at the actual object.

Is it rigid?

Is the surface sound?

Does it flex?

Is it intended for indoor or outdoor use?

And can you prepare the surface properly for your adhesive?

When in doubt, test your adhesive on a small, inconspicuous area before committing hours of mosaic work to the project.

The Shoestring Rule

One of the goals of this Mosaic on a Shoestring series is to help you spend less money without sacrificing the quality of your work.

That means looking for inexpensive and creative solutions.

But it also means learning when not to use something.

Mosaicing directly onto your kitchen wall isn’t a bargain if the drywall fails.

A $3 plastic object isn't a bargain if the adhesive fails.

And a thrift-store find isn't a bargain if you spend 20 hours mosaicing it only to discover that the base wasn't up to the job.

Before you start gluing tile, take a few minutes to think about the thing underneath it.

Your mosaic is only as good as the foundation you're putting it on.

Sometimes the best way to save money is to spend a little more on the base—or choose a different base altogether.