NEAT CEMENT is the term applied to cement mixed with water without the addition of any sand or gravel. Neat cement produces a very smooth surface and responds to reproducing every change in the surface of the model. It should be used on the surface only and not for the entire tile or pottery. If used without any sand or gravel, it is termed “too fat,” and has the fault of cracking sooner or later. Therefore neat cement is always backed up with a concrete mixture.

CONCRETE is a mixture of sand and cement, gravel and cement, or rock and cement. In all instances where such a mixture is made, the two parts should be mixed dry before any water is added. Only enough should be mixed to meet immediate needs as it is not best to use cement that has stood so long that it has commenced to harden.

TO SECURE A VERY FINE SMOOTH SURFACE for tiles or pottery the cement should be used neat. It must be sifted dry through a fine sieve and enough water added to make it of easy working consistency. Then a mixture of two-thirds gravel or sand and one-third cement with water added may be used on the back of the tile or the inside of a vase and possibly again lined with a mixture of neat cement.

Cement or concrete can stand for an hour or two and again be used by adding more water and mixing thoroughly. This cannot be done with plaster and should be avoided with cement or concrete. If chemical action has commenced and the cement has partly set, it naturally will have lost much of its strength for second use.

A CONCRETE MIXTURE of one part cement and two parts sand or gravel will give good strength. The sand or gravel must be clean. If it contains any vegetable matter or other sediment, it should be avoided. To test your sand quality put a four-inch layer in an ordinary quart jar, fill with water within three inches of the top. Cover and shake well. Then permit the sand to settle. If the sediment or loam which remains at the top of the sand is one-half inch or more, the sand is not fit for use in concrete.

CEMENT MIXTURES ADAPTABLE TO VARIOUS USES are given below. These may be used for backing and reinforcing large problems, in garden pottery, garden furniture or walls.

1. RICH MIXTURE
1 part cement
2 parts sand
5 parts gravel		2. STANDARD MIXTURE
1 part cement
2 parts sand
4 parts gravel
3. MEDIUM MIXTURE
1 part cement
2½ parts sand
3 parts gravel		4. LEAN MIXTURE
1 part cement
3 parts sand
6 parts gravel

Cement and sand mixed dry first, then with water. The gravel is mixed wet with other mixture and thoroughly combined.

Builders use the Rich Mixture for columns and high stresses, and where water tightness is necessary.

Standard Mixture is used for arches, for tanks and sewers, and for machine foundations.