Mosaic grouting... [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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11-30-2008, 12:58 PM
I need to ask some of you SUPER TILERS!!!!! about some floor mosaics. I recently installed some on the floors of a revival 50's home. When I went to grout the first one I got air pockets?? in them that showed up when I went to clean the grout. I ended up going back over the floor after it had set up to remove them. On the second floor I decided to use Spectraloc as the floor as it was going to be used as a childrens bath and to see if that would end the air holes that had shown up in the first floor using unsanded grout. I got some of the same problem which was actually easier to correct with the epoxy. I tried a different float, thicker mix, thinnner mix, slower, faster, etc. I also tried to mix crete powder with the grout and get it all done at once, but the darn paper backing would let go once it got wet. :cry: Same result. The mosaics were 1/2" square with a 1 1/2" hex. Any ideas? Not a terrible problem, but a pesky one.

Thanks, Mike

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11-30-2008, 01:24 PM
Hey Mike,
I'm not really a "super tiler" but I'll try to help. :D
Sounds to me like more of a grout problem, I don't think it has anything to do with the fact that you're grouting mosaics. I think you're getting air in the grout as you're mixing it. Are you mixing it by hand? If not you may want to try that. Also make sure you let it slake for about ten minutes then remix it. Don't add any additional water to it after you do this. Slaking makes a world of difference.
You also need to make sure that you are pressing the grout firmly into the grout lines - filling them completely up.

11-30-2008, 01:43 PM
its actually in the way your are floating the floor.

you need to spread the grout over the area, go back over it with the float held at more of a flat angle and then go back and cut it off with the side edge. this will ensure you have pushed the grout down in the joints and have no air pockets.
you can also use a drum stick on larger tile to make sure it's pressed down, but I prefer floating it a few times like I described.

11-30-2008, 02:24 PM
slaking can make or break your grout job. i hold my float at so many different angles but it comes so natural to me i dont think about it i like to press it into the joint and then go back over it 2 more times at a 30 degree angle too then i proceed and keep going.

11-30-2008, 03:33 PM
The key word was UNsanded grout. Never, as far as I'm concerned for mosaics. Not that you can't havre pinholes with sanded. Stiff mix, slake, proper float technique, you will still get a few. It's grout, another work for "process to screw up a perfectly good installation". :)


11-30-2008, 04:44 PM
hey good eye i missed that. i hate unsanded grout its just so sucky and those stupid dye smears but its nice for marble and granite floors when floated properly.

11-30-2008, 05:16 PM
Damn Gueuze,
You got it. I completely missed that one. That seems to be the major part of the problem. UNsanded grout will always bubble. It's not a problem if you're using it in 1/16 grout lines but anything above that is going to create problems.
Get some sanded grout. Gueze solved your problem. :D

11-30-2008, 07:34 PM
SCtileguy and Supertilers,

These two grouts pinhole for different reasons.

Unsanded grout is often cleaned to early, on any tile but wall tile. Because the unsanded grout is cleaned before it is set up (no transfer when touched) it is easy to reemulsify the mix and add water to the nonsanded grout, at least at the surface. Then when you go to do final clean up there are pinholes to deal with. Also, because they are nonsanded, it takes more mixing to break up the pigments. This can entrain air into the mix.

Epoxy grout can also be over mixed adding air, but more often; it is due to the setting of the tile. Epoxy cures by heat. After the grout has been floated, as the heating occurs around the tile and grout joint is often forces the cold air under the tile, out. Leaving a bubble or pinhole. This can be greatly reduced by increasing your coverage of setting material at the time of installing the tile. No voids, no air, no pinholes.

My two cents. I hope it helps.


The Kid
11-30-2008, 08:16 PM
When ever i use unsanded, I let it setup for alot longer then i would sanded grout. let it get real firm then come back with a doodle bug to tool it, and then finish with a sponge. Ive had good results with this method. :)

11-30-2008, 08:33 PM
Rick- LOL at the new sig line!

Oh, I've been immortalized! :neesie:

My name is man. Gueuze man. I like my groutini's sanded, and stirred.


11-30-2008, 08:43 PM
i just decided to change my name too, its been a weird day

11-30-2008, 10:55 PM
Thanks to all for the advice. Glad to know that I am not alone in my dislike of unsanded. For the record, I do hand mix all my grouts. Frank (helper) hates me for this. He said he can't fit a margain trowel on the Milwaukee--hehe!

Anyway, thanks again.


Square pusher
12-01-2008, 01:41 AM
When I started in the the trade all I did was grout and cut for about two years, so I had a lot of time to learn from my mistakes.

I like to dry mix 2 parts sanded and 1 part unsanded, sometimes a 50/50 mix depending on the size of the joints.. It seems to go in a lot easier and reduces the amount of pinholes.

If you do this make sure you dry mix enough the first time.
or you might end up with areas that are slightly different colors.

I also find that the wetter the mix the more pinholes you get.
Sometimes it's worth the extra effort to use a bit of a dryer mix.
I hope that helps.