I have made a video about how to mix up small amounts of powdered products like grout and thinset with minimal dust and mess.
I worked briefly as an engineer in an advanced materials testing laboratory with exotic and toxic materials, and I have put some thought into the methods I show in the video.
Notice in the video how I keep my hands, trowel, and bucket clean throughout the scooping and mixing process.
The method I show also minimizes the amount of dust that is created.
I should be wearing rubber gloves as I do this because powdered stone products such as grouts and mortars are caustic, abrasive, and dehydrating.
I omitted gloves only because I’ve done this a few million times.
Please share this video with your friends because it has relevance outside of mosaic and can help people work more safely.
The Video
The Captions
The first step is to wet the work area thoroughly to insure that the air is humid.
Humid air precipitates dust much more rapidly than dry air.
Now I am scooping the powdered thinset mortar into the mixing bucket slowly and carefully. NEVER POUR POWDERED STONE PRODUCTS.
Notice how I carefully lower the cup into the mixing bucket and slowly TILT AND SLIDE the powder onto the bottom of the bucket.
Do this instead of pouring the powder.
Of course I am wearing an N95 mask while I do this, but masks don’t protect your clothing or workspace, and eventually the mask comes off.
As soon as I have scooped enough powdered thinset mortar, I seal its container and mist the work area thoroughly. The purpose is to catch any dust hanging in the air.
Notice I also misted the powdered mortar in the mixing bucket.
All of the water I add to the mortar will be added by misting and sprinkling.
Misting has to come before sprinkling because even sprinkling can cause puffs of dust.
Once I have added some water, I gently turn over the layer of wet to expose the dry material underneath.
Then more water is added by misting, then sprinkling.
Once again I turn the wet material over gently. I do not stir rapidly.
I should be wearing rubber gloves as I do this because powdered stone products such as grouts and mortars are caustic, abrasive, and dehydrating. I omitted gloves only because I’ve done this a few million times.
The cycle of wetting and turning over is repeated as long as dry material can be found.
I don’t measure the water I use.
Instead of measuring, I add water slowly by misting.
As dry powder become more scarce in the bucket, I stop using the jug to sprinkle and only use the mist bottle.
Notice that I am NOT cleaning my mixing trowel on the edge of the bucket.
Instead of doing that and getting mortar all over my hands, I use a second spreading tool (paint scraper) to clean the trowel.
Spreading tools such as trowels and palette knives are used in pairs so that they can clean each other.
Once I can’t find any more dry material in the bucket, no more water is added, and the work of busting up lumps begins.
Notice how I scrape the edge of the bucket to keep the mortar from smearing higher up the sides of the bucket.
Scraping the sides and keeping the rim of the bucket clean is the key to containing the mess.
You also need to periodically clean the spreading tools on each other, or your hands will get fouled and spread the mess.
The work of busting up tiny dry lumps in the mortar is a lot of mixing taking care to emphasize the bottom and sides of the bucket.
The desired consistency of grout is a stiff dough. I prefer my thinset mortar about the same only slightly thinner.
More dry powder and more water can be added to adjust the consistency if needed.
Let the mortar or grout sit for five minutes and then stir again before using the material.
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