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Or, if the work is being finished for a day and is to be
covered for the night and resumed the next day, the mortar is cut away
to the edge of the finished part of the mosaic before being covered.
Next day, before placing fresh mortar next to it, all the edges should
be carefully wet down to insure bonding.
. . . mortar mixture
Use a formula of 1 part of Portland cement to 2 parts of fine sand,
with only enough water to allow the mixture to spread easily but not
to run. Add a little water at a time and mix it in well; then add a little
more until the proper consistency is reached. Some craftsmen like to use
a bit of lime putty or fire-clay in the mortar mixture to prevent its setting
too quickly and also to make it more workable. Proportions suggested
are: 3 parts Portland cement, 6 parts of sand, 1 part of fire-clay or lime
putty. Check with your building materials dealer for the availability
of these materials.
Lay the mortar to a depth of 1/2 to 1 inch, depending upon the size of
the pebbles. Remember that if the mortar is too loose and wet the pebbles will sink into it and be lost. If the mortar is too stiff, the pebbles will
be difficult to insert in it deeply enough to engage the mortar and make
a secure bond. A little practice will enable you to work out just what
stiffness and what depth to make the mortar. As your adeptness increases you will be able to increase the size of the area on which you
work, but remember that most cement mortar will set within an hour
or so, and by two hours will be getting really hard. It is a good plan to
keep the area fairly small, thus avoiding disappointment, wasted mortar,
or the risk of its not bonding properly and having to be ripped out and
alone over.
. . . method of working
The pebbles will bond better with the mortar if they are inserted wet.
Some craftsmen keep them in cans of water (the cans in which they
have been sorted for size and color will do nicely), and thus keep dust
and dirt off them so that they will be fresh and clean when they are
placed in the mortar. The moisture will aid in creating a strong bond,
too. Lay out the design divisions in advance so that you can plan ahead
which areas to work on in each session. In the case of steps, for instance, you can do a step at a time, unless they are very broad or very
long.
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