MORTAR-MAKING. 901 



From the conflicting' opinions on the subject of sand, we 

 may conclude that in making- ordinary mortar our ]n-esent 

 knowledge and experience would not justify any great expense 

 in order to procure sand of any particular colour or grain, or 

 from any particular source, but that generally sand either too 

 coarse or too fine should be avoided. That for ordinary 

 buildings we should, if possible, use river or pit sand in 

 preference to sea sand ; but if any great saving is effected in 

 using the latter we should not hesitate to do so, taking the 

 precaution to wash it carefully first. That for hydi'aulic 

 buildings and general foundation works, sea sand is just as 

 good as any other when making mortar with hydraulic lime. 

 That in all cases it is worth while to take pains to clean 

 the sand before using it or to make sure that it is clean — i.e., 

 free from earthy particles. 



In applying mortars the first great point to be attended to 

 is the necessity of thoroughly wetting the materials to be 

 joined. If the moisture is suddenly drawn off" any hydraulic 

 mortar it will not harden. Dry bricks and most stones absorb 

 a large proportion of water, so that if mortar is applied to the 

 dry surface of a brick and another pressed on it the Avhole 

 of the moisture will be squeezed out of the mortar and taken 

 up by the bricks, and the mortar itself will crumble into 

 powder ; whereas if the brick is thoroughly wetted it will be 

 able to absorb no more moisture, and the mortar will set as it 

 ought. With many compact stones it will be sufficient to 

 water the surface at the moment of using them, but porous 

 materials, such as sandstones and bricks, especially of the 

 ordinary plastic inake, should be allowed to soak in water 

 for some time before use. All professional men and even most 

 ordinary bricklayers know these particulars full well; but 

 strange as it may seem to state, a great proportion of them are 

 unaccountably careless in this respect, and feel quite satisfied 

 when having seen a few bucketsful of water dashed over a 

 heap of bricks, whilst presumably the bricks in the interior 

 of the heap have hardly been even damped on their 

 exterior. 



The next requisite in applying hydraulic mortar is that the 

 mortar should be as stiff as it can be used without incon- 

 venience, and without the risk of all the unevennesses of the 

 joints remaining unfilled when the bricks or stones are forced 

 home. The third requisite is to prevent rapid drying of the 

 mortar after it has been applied. 



Mortar is sometimes applied in a form termed " grouting," 



