mixing thinset [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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02-28-2002, 11:33 AM
When you mix up your thinset, do you mix the whole bag? I understand about not spreading more than you can cover w/ tile in 15/20 minutes, but won't the mud start to set up in the pail if you're working for a couple of hours with the same batch? Thanks again for all the help. This board has saved me from the wrath of the wife more than a few times already.

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02-28-2002, 12:07 PM
Whether or not to mix the entire bag is a function of your layout and how quickly you can get it done. Thinset does not set up as quickly in the pail as it does on the spread on the floor. Set up is based on humidy, temperature etc. There is no point in mixing the whole bag just to do it. Simply cut your H20 ration accordingly and mix a quarter, half etc.

02-28-2002, 01:32 PM
I would not mix up the whole bag at once, only what you can tile in a couple of hours, which is the pot life of the mortar I use (Custom Master Blend with Custom Acrylic Admix).
I am not a speedy tiler (only a weekend warrior) and do not try and tile over, maybe, 15 square feet at a time, as it takes me a good deal of time to set the tile and check each for alignment (both side to side). This is probably pitifully slow, compared with the pros, but I am not having to make a living doing it. My standard measure for 15 square feet of tile (with a 1/4" X 1/4" square notch trowel) is to fill one standard coffee can (meant for 12 dry ounces of ground coffee) with acrylic admix, dump in a bucket, and mix with dry mortar until it forms a spreadable, pretty thick mixture that will not fall off my mixing blade when lifted out of the bucket. This amount will usually adequately conver the area, with maybe 20% left over. You could use a little less, if you don't want to waste mortar. Good Luck.

Bud Cline
02-28-2002, 03:03 PM
Based on the intricacies of your layout you can mix your thinset amount accordingly. You will get a feel for how far and how fast you can go. Mix what your comfortable with.

Modified thinsets have plenty of pot life but still you wouldn't want to mix a weeks supply at one time.

Rob Z
02-28-2002, 08:13 PM

You may wish to reduce that open time of the thinset before setting tile in it. In my experience, 15 or 20 minutes is too long for thinset to be combed out before a tile is set in it (especially over a mud bed).

I try to spread out only what I can cover within a matter of minutes.

02-28-2002, 08:57 PM
When tiling floors, I put about 2 1/2 -3" of water in a 3.5 gal bucket. Add latex mod mortar to make a peak of mortar with a little water around the edge. Mix and make adjustments. Almost always works out where a full 3.5 gal. bucket of mix is 33-34 lb. of mortar used. Three buckets always 2 bags. With 1/4x3/8 trowel I get 55-60 ft. per batch, 75 ft. with 1/4x1/4 under board. Stir now and then, will stay useable for hours, depending on type of surface and ambient temp.


Paul D.
02-28-2002, 09:04 PM
Hey Kelsner,

For us rookies, mixing more small batches is much safer, I've found. 'Specially when you're using that $30 per bag stuff.

The coffee can measuring Keith suggested is a good trick. One thing I learned after the fact, is that if you are using an acrylic modifier, mixing thinset in a bucket that has residual from the last batch will shorten the pot life. I think the instructions said that, but I seem to remember learning it the hard way. Just keep two or three buckets ready, and fill the newly emptied one with water whilst you mix the new one. You could even measure out dry material in a couple-three buckets at once. Good luck...

John Bridge
03-01-2002, 04:37 PM
For all you engineering types and other college boys, mixing thin set in a bucket that is encrusted with previously used thin set invokes what is known in the trade as the "scratch coat effect." Takes us back to the old days of plaster walls and shower stalls.

A scratch coat is applied to the lath on a particular day. A couple days later, you come back and apply a second coat of mortar. If you do not wet the previous "scratch" coat, your new coat will try to set the minute it is applied.

The point (finally): Wet the inside of the bucket before you begin your mix. :D

Paul D.
03-01-2002, 05:23 PM
Oh yeah, John....the old thinset must provide a nucleation site for the mix to begin to crystallize or polymerize...whatever it does. Kind of like scratching the side of the beaker in chemistry class to begin precipitation from solutions. ;)

Just wetting it will prevent that from happening?

Wait! What's this scratch coat stuff? I though mortar would not stick to mortar. Wasn't that why you spread a little thinset on a mortar surface prior to adding mortar to level up a cavity or something?

Rob Z
03-01-2002, 05:40 PM

Attaboy! This should keep Bud busy for an hour or so!

"...a nucleation site for the mix to begin to crystallize or polymerize..."

03-01-2002, 06:27 PM
What is the name and model no. of a drill you can use to mix thinset. I've burned up two drills so far. THANKS

03-01-2002, 07:04 PM
Try a Milwaukee Hole Hawg. Use the low 300 rpm speed for mixing.

Others use low rpm high amp drills. Lower the rpms the better for maintaining bond strength of the thinset. Entraining air weakens the bond greatly.

Rob Z
03-01-2002, 08:09 PM

Take it over to the Deep End...

John Bridge
03-01-2002, 08:25 PM

Rob's runnin' us out of here, so I'll start something in the deep end on cement sticking to cement.

See ya there. :D

03-01-2002, 08:35 PM

I use a 1/2" Dewalt drill for mixing thinset and grout. I have no problems unless I try to mix a full 5 gallon bucket of thinset. I usually mix 1/2 to 2/3 of the bucket. No issues with the drill in these conditions

If I could afford a Hole Hawg, I would take that route. they are a pretty price at $250-$300


Rob Z
03-02-2002, 04:40 AM
I have a 1/2" Milwaukee Hole Shooter and a fairly small mixing paddle. It works for up to about a half bucket of thinset.

I use my Milwuakee right angle drill with a much larger mixing paddle for full buckets of thinset.