Monthly Archives: September 2013

How To Fix Grout Mistakes

In my previous post, I wrote about how to remove and replace glass mosaic tile to make changes to a mosaic before you grouted it. I also explained why it was good to display the mosaic for a few weeks before grouting so that you had a chance to see the mosaic as a whole with a fresh eye before setting it in concrete.

But writing this got me to thinking about a common problem that isn’t visible until you grout the mosaic, and that got me to thinking about all the ways in which people “ruin” their mosaic in the grouting process. Fortunately, the mosaics aren’t actually ruined, and there are solutions to each problem, at least in the vast majority of cases.

Conventional Grout, Not Epoxy Grout

Keep in mind that all of the mosaic advice on my websites is written for conventional portland-cement grout. If you are using one of the new epoxy-based grouts, then some of what I am recommending might not be possible or might require more work.

Ways Mosaics Are “Ruined” By Grouting

Here are problems commonly reported after grouting a mosaic:

  • My mosaic is covered with a dull gray or white haze.
  • I let the grout harden on top of my mosaic before I could get it off.
  • There are specks of grout in the pits and voids of my glass tile.
  • My grout is crumbling and falling out.
  • The grout stained my unsealed stone or ceramic tile.
  • My grout is not as dark and colorful as it was when it was wet.
  • I used the wrong color grout.
  • My tiles seem smaller after grouting, or my mosaic isn’t as colorful as it was.

NONE of the above problems mean the mosaic is ruined permanently, and most are relatively simple to fix.

A Dull Gray Or White Haze

Grouting involves pressing wet grout onto the surface of the mosaic, working it into the gaps
thoroughly, and then scraping off all the excess. But that is just the initial phase of the grouting process. The second phase involves cleaning and hazing, both of which must be done with care not to erode the grout from the gaps or moistening it with excess water.

If your sponge or rag contains too much water, then you wipe off the top layer of colored grout in the gaps leaving only the sand, and then the grout will look lighter than intended when it is dry. That is why installers only clean the tile so much when the grout is still wet and curing. They err on the side of caution and leave a thin residue that dries into a haze. That is why the process of buffing a freshly grouted mosaic with a clean rag is called “hazing.”

If you leave a little too much residue, the haze might be more substantial and not wipe off with a rag. If so, no worries. Simply use a Scotchbrite pad or wire brush to scuff away the haze. Do this process wet using a spray bottle to mist the mosaic to avoid breathing dust.

The Grout Hardened Before I Could Scrape It Off

This problem can be thought of as an extreme case of the problem discussed above. If you have excess grout hardened on your mosaic, it can be removed. Concrete can be eroded relatively easy if the total surface area isn’t excessively large. For this situation, we has a wire brush of the type used to clean welds, which has thicker and stiffer bristles than the wire brushes used for cleaning barbeque grills. We mist with spray bottles, and once the excess is worked off, we finish up with Scotchbrite pads and rags as described above.

Specks of Grout In Pits

Sometimes stained glass and even molded glass tile will have pits in the surface that were bubbles when the glass was molten. Naturally grout fills these voids just as it does the grout gaps, and it doesn’t wipe off. Often times, people won’t notice the problem until the grout is cured and lighter. This is a trivial problem. Mist the mosaic with water and use a dental pick to clean out the voids. You can also use a light gauge wire brush if the problem is fairly widespread, but take care not to erode grout from the gaps.

Crumbling Grout

Concrete hardens by binding water, not by drying out. If you doubt this, then think about how concrete can harden underwater. If you let your grout dry out when it is curing, it will be soft and crumbly. Cover your mosaic with a plastic trash bag if the AC or heat or sun is making the air dry. The grout will also be soft and crumbly if you don’t add enough water when you mix it up. Follow manufacturer instructions on the package.

If you have crumbly grout, then scrape it out with the grout removal tool we sell or an old screwdriver and regrout the mosaic.

The Grout Stained My Tumbled Stone or Unglazed Ceramic Tile

Porous materials like tumbled unpolished stone and unglazed ceramic tile can be stained by grout. We prevent this problem by wiping the mosaic with a rag dampened with Tile and Grout Sealer, such as TileLab brand a day BEFORE we grout. We are careful not to get any sealer in the gaps where the grout will need to bond to the sides of the tile, and we have used small artists paint brushes for this purpose.

If you didn’t know to do this, all is not lost. You can sand off the stained layer with 80 grit sandpaper followed by 120 grit and finer grits if needed. Of course, you don’t use sandpaper. Like any craftsperson in the know, you buy the belts used for belt sanders and cut them up. The belts don’t cost much more than sandpaper, but they last literally a hundred times longer.

Also, you should wet sand this using a spray bottle to mist and wear a dust mask to avoid breathing the silica dust.

The Grout Is Lighter Than It Was When Wet

Grout will always be lighter when it is cured and dry, no matter how dark it was when wet, and this is particularly true for dark colors like charcoal black.

There are two solutions:

The first option is to seal the grout with a sealer known as a “stone enhancer” instead of a regular tile and grout sealer. However, enhancers are invisible pore sealers just like regular grout sealers and not a coating that actually forms a gloss layer over the top of the grout. That means there are limits to how much color you can bring out with an enhancer.

If you need an extra dark grout gap, then consider painting it with artist’s acrylic paint instead of sealing it. Glass tile is non-porous, so the paint should wipe right off the glass and stick only in the porous grout. Of course, you should only do this for dry indoor mosaics. I don’t want to get any emails from dodo birds painting the insides of their tile showers.

The Wrong Color Grout

Grout can really change the look of the mosaic, especially if you use wide grout gaps. Grout works best when it serves to separate the tiles visually like a thin pencil line in a watercolor painting. That is why the best choice of grout color is usually a medium gray, unless you are using gray tile. It’s important that the grout color CONTRAST tile color instead of matching tile color. If it matches the tile color, then the tiles will run together visually and not stand out as individual tiles, and the mosaic usually looks poorly as a result.

There are two alternatives when you use the wrong color to grout your mosaic: Scraping the grout out with a grout removal tool or painting the grout with color as described above.

My Tiles Seem Smaller or My Mosaic Isn’t As Colorful

The grout gap always looks wider once it has grout in it. It also has no color until you fill it up with concrete. In an ungrouted mosaic, the colorful sides of the tiles are visible. That means a mosaic with wide grout gaps is particularly susceptible to looking duller when grouted.

Smaller Grout Gaps For Smaller Tile

If you use small tile or small pieces of tile, then remember to use a correspondingly smaller grout gap. Sure, a 1/16 inch gap is standard, but if your tile is 3/8 inch, you probably want to use a smaller grout gap if you are rendering the details of an image instead of merely tiling a wall.

Rounded Tops

Another solution is to not fill the grout gap all the way to the top. This is particularly important when using tile with rounded corners or a rounded top surface. Think of it this way: If you let only the peaks of the tile show above the grout, then your mosaic’s surface area will be mostly dull concrete instead of colorful glass.


If you haven’t yet grouted a mosaic with wide grout gaps, consider reworking the areas with the widest gaps. Often that isn’t practical because the problem is widespread, so the remaining option is to rub the wet grout off more aggressively than normal when you scrape away the excess and try to erode some of the grout from the tops of the gaps.

If you have already grouted the mosaic, then consider using the grout removal tool to scrape some of the grout from the tops of the gaps. This is particularly effective when the tile used has rounded tops. If you get some of the grout off the slopes of the tile so that more of the faces are  showing, then the mosaic can become a lot more colorful. Again, this isn’t as useful an option if the mosaic is wet or outdoors. In those cases, you would have to pay close attention and make sure that enough grout remained to keep the out moisture, and you would need to reseal the mosaic.

Don’t Give Up Hope

It is an act of faith to dump wet concrete on top of a detailed picture that you just spent weeks making by hand from tiny pieces of glass. Not surprisingly, most novices expect the worst when anything goes wrong or appears to go wrong, and they are usually convinced their mosaic is ruined. This simply isn’t true.

Procrastination Before Grouting Is A Virtue

The Pace of Art

Taking time to reflect on what you are doing can be the difference between producing a mediocre work of art and a great work of art. All too often, we miss opportunities to make something really wonderful because we are too concerned with just getting the job done. When we work on our art at the same pace that we run errands and do other tasks in the modern world, we end up making artwork that is more product than art.

It Takes Time To Really See

Like many artists, I have trouble seeing a work of art as a whole while I am actively working on it because I am too focused on the details of specific areas or specific aspects of the work. Ironically, these details usually don’t turn out to be nearly as important as something I’m not even paying attention to at the time. That is why painters let “finished” paintings hang out in their studios for a few weeks before applying the final varnish. After you are supposedly done is when you usually see what needs to be done.

Display Your Mosaic Before Grouting

I always display a mosaic in my studio for at least several weeks before grouting it. Before things are literally set in concrete, I want to look at the mosaic with fresh eyes and really see it for the first time. Most often I notice little things, things that might be good to do on the next mosaic or things that aren’t significant enough to justify the work required to change them. But other times I notice fatal flaws, things that make all the difference in the world and have to be changed. What do I do then?

I have written a post about how to remove and replace glass mosaic tile to change mosaic designs before grouting.

How To Change A Mosaic Before Grouting (Or Afterward)

Already Grouted?

If you have already grouted your mosaic, you can still use these instructions, but you will first need to remove the grout using a grout removal tool, which is normally used to scrape grout from the gaps between glazed ceramic tile. It may take a little more care with glass, but this tool can be used to remove grout from mosaics made from small pieces of glass tile.

How To Remove and Replace Glass Mosaic Tile

A Caveat

Glass tile doesn’t usually pry up in one piece. If you are able to get most tiles off in one piece, then there was probably something wrong with your adhesive or mortar. Expect the glass to come up in sharp pieces and slivers and not be reusable. Never chisel the glass off by banging at it forcefully. If your scraping tool slips past the tile being chiseled, your knuckles and wrists will be headed straight toward razor sharp teeth mounted in concrete. Wear leather work gloves. I wear my welding gauntlets.

Moisture Helps

If the mosaic in question was made with a white PVA adhesive such as Weldbond, then I use a moistened cotton swab to selectively wet the edges of the tile, taking care not to wet the surrounding tiles too much. Note that if the Weldbond has had several months to cure, it may be more water resistant, but you should still apply water. Keep plastic kitchen wrap such as Saran Wrap over the tile and reapply moisture as needed to let the glue soften for an hour or two.

If the mosaic is an outdoor or wet mosaic made with thinset mortar, moisture doesn’t really help. For thinset mortar, it is best to make any changes within a week at most. Thinset is hard and tough and it really grips the glass once it has had a chance to fully cure.

Prying Tools

I usually use a medium size standard screwdriver to pull the tile up with a combination of scraping and prying. Notice that when you attempt to pry the tile up, you tend to use the surrounding tile as a fulcrum on which to rest the screwdriver, and this is a problem. It can crack or even shatter the surrounding tile, and it is likely to do so because the glue is usually stronger than the glass. Fortunately, there is a simple solution: Lay a Popsicle stick or ruler over the surrounding tile and use that was your fulcrum. Of course, you will need to use one hand to keep the ruler from sliding back slightly as you pry. If you let the screw driver slide the ruler away, it will make contact with the tile underneath and damage them.

Damage To Backers

Plywood and concrete backer board aren’t as strong as Weldbond and thinset mortar, so they will sometime delaminate when use start prying and scraping and you end up pulling off the top layer of the backer. If this happens, don’t panic. Plywood can be patched with a mixture of sawdust and Weldbond, and concrete backer board can be patched with thinset mortar. However, you can minimize the possibility of this happening in the first place by attacking the tile from multiple angles instead of just working from one side.

Safety Requirements

When you pry up glass tile that has been glued down, sharp pieces can break off and go flying across the room. (I try to keep my leather work glove over the tile to prevent this possibility.)

You should wear safety glasses with side shields. You may even want to wear the plastic safety shield masks that are made for working with power tools. You also want to make sure anyone else around your work area has proper eye protection.

Another issue is the tiny sharp slivers of broken glass. Keep a vacuum nearby and use it periodically to clean the work area. It is always the tiny invisible slivers that cut you when you wipe the work surface clean with your hand. Use a vacuum instead.

Wear leather work gloves and be cautious of jabbing forcefully at the tiles. Use deliberate motions and think about where your hand will be headed if the tool slips off the tile: The freshly broken glass is sharper than any steel razor and it is mounted. If you punch your hand or wrist into it, you will be going to the emergency room in all probability.

How To Mix Up Concrete, Mortar and Grout Without Creating Dust

Concretes, mortars and grouts have the potential to create significant amounts of dangerous dust when the water is first added. There is only 1 part water for every 4 parts concrete by weight, so much stirring is required before all the dry concrete will be wet. In fact, you can create a lot of dust just by pouring the water in too rapidly or from too high above the powder.

But it is possible to mix up concrete inside a workshop or studio without creating very much dust and collecting what dust you do create.

How To Stir In The Water

The water should be poured gently over the top of the powder. Pour the water from a low height and pour it gently against the wall of the container. Stir slowly, spreading the water over the top of the dry material instead of digging into it.. Keep the growing blob of mud over the top of the dry stuff. Gradually use your spoon or scoop to slowly scrape into the dry materials until the blob absorbs it all. Make sure you get all the pockets of dry stuff in the bottom corners.

Tips Useful for Batches Large and Small.

Dust Mask

Always wear a dust mask when pouring and mixing dry powders, especially when mixing up concrete products.

Humidifiers and Spray Bottles

Use humidifiers and misting spray bottles to control dust generation, but keep them away from electric power tools to avoid electric shock.

  • Locate the humidifier in the room, not where you are actually working.
  • If your hand or glove gets wet while handling a spray bottle, dry it with a rag before using drills, mixers, etc.

 HEPA Shop Vacuum

A dust mask isn’t going to protect you if you spread the dust all over your clothing or work space. A few days later you will move a box or a board and breath that same dust right in. Buy a HEPA shop vacuum and use it regularly. Use a vacuum bag to protect your HEPA filter, as always.

How To Get Concrete Out Of The Bag Without Pouring.

Pouring dry powders and chips from bags creates more dust than is necessary. Concrete should be scooped or shoveled from partial bags or whole bags should be lifted off similar to how a person takes off a shirt. Misting bottles or HEPA shop vacuums are still required.

For Small Batches

For small batches (and anything else under a full bag), scoop your material from a bag which is kept stored in a plastic bucket with snap-on lid. Use hand shovels, coffee mugs, ice scoops or whatever you have to scoop it out of the bag-in-bucket. Old coffee mugs and serving spoons from thrift stores can be left inside the bucket for next use.

For Whole-Bag Batches

  1. Sit the bag on one end of the bag in the tub or mixer. Make sure the bag is leaning against one wall of the tub.
  2. Slit the bottom seam or panel. Make an X-shaped cut on the bottom panels of concrete bags so that the hole opens evenly from the center of the X. Or cut 3 sides of the bottom panel so that it falls open like a door.
  3. Cut open the top seam or panel of the bag so that it can breath in air as the powder exists from the bottom.
  4. Lift remaining bag off like a sleeve off a column of powder.

Remember to cut the top open in step 3 so that the material slides right out.

Careful With Shop Vac

I usually keep my shop vac running while doing this, but I am careful where I place the nozzle.
Suck in the dusty air but avoid piles of dry concrete. The elephant will eat those as well, and
while that is happening, your vacuum is a machine for keeping the air saturated with very
fine dust, which is bad.

Tell your vacuum to use its powers for good not evil. If not, the first time you drop the nozzle to grab or lift something, it will go straight for the open bag of concrete. Or bucket of nails. The elephant is always hungry. He’ll eat anything he can suck up his nose: Tape measure. Keys to the truck.

How To Dispose of Acrylic Paint Rinse Water

Why You Shouldn’t Pour It Down Drains

Acrylics are a great alternative to traditional oil paint because they are water based, and so there aren’t any fumes, and you can clean up with soap and water. However, at the end of a studio session, the jar or container that you use to rinse off your brushes between colors will have quite a bit of paint in it, and you should not pour this rinse water down drains because many professional-grade paint pigments are toxic, such as the cadmium oxides used for reds, oranges and yellows. Even if you use “non-toxic” student-grade paints, the pigments and acrylic polymers are still problematic for the waste-water treatment processes, and so these shouldn’t go down the drain either.

Disposal As Solid Waste

The solution is to dispose of the material as solid waste. The question is how do you get the water out, which isn’t as simple as just letting it dry out. You may have noticed that rinse water from acrylic paint tends to dry much more slowly than regular water. This is probably due to the acrylic polymers forming an invisible scum on top of the water which acts as a barrier that inhibits evaporation. But there are ways to help the water evaporate faster.

How To Dehydrate Rinse Water

My preferred solution to how to get rinse dehydrated is actually a set of solutions that take advantage of waste energy or ambient energy.  In the winter months, the rinse water can be poured into a metal coffee can or other recycled disposable container and set on a steam radiator. You can also pour it into a disposable aluminum baking pan and sit it by a heater vent or AC vent. In the summer months, there is the floorboard of your hot car with the window cracked open slightly.

I use an old plastic tote that is wide and shallow. This allows the rinse water to spread out and maximizes surface area. I keep the top covered with 1/2″ hardware cloth (wire mesh) to keep out pets and leaves.  If I am painting a lot every day and generating more than my usual amount of  rinse water, I will sometimes put my dehydrator tote next to or under a fan, preferably one that was already running and not turned on just for my rinse water.

Of course, I don’t try to clean out my dehydrator tote between uses. That would be problematic for several reasons (such as the potential to create hazardous dust), so I just have thin layer after thin layer accumulate on the bottom of my dehydrator, which will eventually have to be disposed of and replaced after several years.

Golden Paint’s Recommended Solution

Golden is the leading manufacturer of acrylic paints and mediums, and their website is a tremendous resource of how-to information. They have written a page explaining how to use hydrated lime and aluminum sulfate to quickly precipitate paint solids from rinse water and then filter them out using coffee filters. Keep in mind that hydrated lime and aluminum sulfate are commonly available in the fertilizer aisle of your local hardware store or land and garden center, so we aren’t talking about exotic chemical reagents that you need to special order.

Golden Paint’s Demonstration Video

Golden also has a video on YouTube demonstrating how to use their method to precipitate and filter the solids, but I think the demonstration could be improved. Specifically, they show the reagents being poured from bags, which should be avoided in general because pouring creates so much dust. Instead of pouring, slit the top of the bag completely open and scoop from the bag using an old spoon or scoop or hand shovel. There is another useful point they could have shown, especially since these powdered reagents are likely to be used intermittently and stored for extended periods:

Use Plastic Buckets With Lids To Store Hygroscopic Powders

Powdered reagents that are soluble in water also tend to be hygroscopic (bind moisture from the air) and clump over time. Examples like sugar and table salt come readily to mind, but the problem can be more than a nuisance. For example, old bags of chemical fertilizer are often unusable because the tiny pellets of fertilizer will “sweat” moisture from the air and fuse into one big lump of material that could never be spread in quantities small enough not to kill plants.

The heavy-duty plastic bags that many fertilizers and powdered reagents are sold in weren’t really designed for long-term storage and offer limited protection over time. Often times, twisting the plastic bag closed with a bread ties isn’t enough to seal out the moisture from the air. Sometimes all it takes are a few tiny holes in the bottom of the bag, especially if the material isn’t consumed for months. That is why I save old plastic pails and buckets with lids to store things like grout and thinset, and I would probably recommend them for anyone using lime and aluminum sulfate for precipitating the solids from their paint rinse water. Plastic buckets with snap-on lids are relatively cheap, and you can also get them for free from restaurants, bakeries and house painters.


Scoop from the bag-in-bucket. Cut or fold the bag down as needed.