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Old 12-20-2010, 01:04 AM   #1
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How do I mix Mortar to get right consistency

Im using Mapei utlraflex1 Mortar to lay 18" ceramic tiles on a cement dining room floor. Im getting it too wet or too dry and have to throw away alot of mortar. Everyone says to get it to the consistency of peanut butter, I do that and my tiles sink and have to pull them up and try again. I called manufacturer and asked for the right ratio to mix and they wouldn't help me. Does anyone know the right ratio to mix this mortar, or what im doing wrong. Im trying to mix 1/2 of the bag at a time which would be 25lbs.
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Old 12-20-2010, 03:21 AM   #2
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According to the TDS for Ultraflex 1

1. Before starting, take appropriate safety precautions. See
MSDS for details.
2. Into a clean mixing container, pour about 5 to 6 U.S. qts.
(4,73 to 5,68 L) of clean potable water. Gradually add 50
lbs. (22,7 kg) of powder while slowly mixing.
3. Use a low-speed mixing drill (at about 300 rpm), with
an angled cross blade mixer or double box mixer.
Mix thoroughly until mixture becomes a smooth,
homogenous, lump-free paste. Avoid prolonged mixing.
4. Let mixture stand (“slake”) for 10 minutes.
5. Remix.
6. If mixture becomes heavy or stiff, remix without adding
more liquid or powder.

Shelf Life and Application Properties*
at 73°F (23°C) and 50% relative humidity
Shelf life................................................... 1 year
Open time*............................................... 30 minutes
Pot life*.................................................... > 2 hours
Time before grouting................................ 16 to 24 hours
VOCs (Rule #1168 of California's
SCAQMD)................................................ 0 g/L
*Open time and pot life vary based on jobsite conditions.

Long story short, for 25 lbs, put 2.5-3 U.S. qts into clean container, and add powder. Should have 30 minutes to work with it.
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Old 12-20-2010, 06:38 AM   #3
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Neal, what size trowel are you using? If you are using anything bigger than a 1/4" x 3/8" x 1/4" or backbuttering a lot, then you should switch to a medium set mortar, like Custom's Granite and Marble mortar. Thinset should be thin, say no more than 1/4" thick when the tile is compressed into it. Thicker than that, it looses compressive strength and is prone to settling, like you are observing.

Check your thinset for proper consistency by combing it out and observing the ridges. If they stay crisp and sharp, then your mix is fine. If they slump or round over, then you have too much water. You'd rather be on the stiff side, so err on too little water.
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Old 12-20-2010, 08:53 AM   #4
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When I make a batch of thinset, I put the correct measured amount of water in a container and add most but not all to my bucket. I then add the correct amount of thinset and mix well. If it's too stiff after mixing I add a bit more water. The thing I learned here was the importance of good mixing. What looks way too dry at first may be perfect after a minute with the drill and paddle.

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Old 12-20-2010, 09:06 AM   #5
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Originally Posted by Scott
Should have 30 minutes to work with it.
Not right, Scott. The pot life is 2 hours...that's how much time one would have to use the thinset mixed up. The open time is either the amount of time before it should be re-mixed or the amount of time it can be spread and combed before setting a tile. I believe it may be the former.

Wendy is so right about the mixing time. It is more important than most people think to mix the mortar for a sufficient duration of time at the right mixer speed. Mix it too fast or too short and it isn't going to be properly hydrated.
If that doesn't work, I'll always think it should have.
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Old 12-20-2010, 10:42 AM   #6
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Mixing a modified thinset is a two-step process, and the timing and actions taken will greatly affect the resulting mixture. Modern modified (fortified, etc.) thinsets consist of sand, cement, and proprietary mixes of other addatives. Those addatives must hydrate to complet the process. So, you mix it all up for the specified time, then you MUST let it slake (sit) for the specified time. This allows the addatives to absorb the water and become flexible and properly mixable. Then, after slaking (you really DO have to wait the specified time, don't try to rush it!), you mix it again. this second mixing distributes the now liquified modifiers and actually encapsulates the mortar and sand mixture. If you don't do this, the texture and strength are compromised. Most people do NOT mix it per the instructions. The manufacturers spend a lot of time and money researching how to make their product work.

One (rare) thing you might run into when not mixing the full bag is that, while uncommon, it is possible that the mix is not homogenous (not fully mixed), and when you pour out half, you are not getting the proper proportions of all the included ingredients. I've not seen this, but then I've not mixed a huge amount of thinsets. In any dry mixture, it is possible, depending on how it is originally mixed and shipped, for the componet parts to statify, and no longer be mixed up well. SO,for example, you might end up with a lot of addatives on the top, and the sand on the bottom of the bag. Fine if you mix the whole thing, but disastrous if you don't premix the dry stuff first (really tough to do!).

Then, unless you use a scale, it's hard to accurately judge 1/2-bag, so your water quantity can be off. The overall strength and workability of the mix really depends on proper mixing. Using the wrong paddle or the improper rotation rate makes a difference, too. Too fast and you introduce too much air, too slow, and you don't get it mixed properly (assuming you do actually time it).
Jim DeBruycker
Not a pro, multiple Schluter Workshops (Schluterville and 2013 and 2014 at Schluter Headquarters), Mapei Training 2014, Laticrete Workshop 2014, Custom Building Products Workshop 2015, and Longtime Forum Participant.
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Old 12-21-2010, 03:21 AM   #7
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Not right, Scott. The pot life is 2 hours...that's how much time one would have to use the thinset mixed up. The open time is either the amount of time before it should be re-mixed or the amount of time it can be spread and combed before setting a tile. I believe it may be the former.
Thanks for clearing up the confusion. I stand corrected.
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Old 12-21-2010, 10:40 AM   #8
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Really look at your thickness as Bob pointed out. 18x18s, especially depending on how heavy they are are going to be prone to settling on anything but the flattest subloor when using thinset.
Given a slab floor, I wonder how actually flat it is? Any buildup of thinset, especially with a heavy tile, will lead to settling.

If you think you are close to limits for thinset but don't need the full medium like the CBP granite and stone, use Mapei lft or laticrete 4xlt. They can be mixed at any consistency between thin and medium applications simply by varying the water quantity. Really great to work with on those large format tiles.
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