278 



Mortar for Plastering. 



Vol. IV. 



John Davy, who edited the last edition of 

 his brother Sir Humphrey Davy's agricultu- 

 ral chemistry, states an experiment made by 

 him to determine this point, which resulted 

 in showing the anti-septic effects of lime ; 

 and HayvvarJ, who wrote a very interesting 

 and valuable work on agriculture, states un- 

 equivocally that lime is an anti-septic. 



Davy says, "the manner in which lime 

 acts in agriculture, requires further and mi- 

 nute investigation, and is a most important 

 subject for inquiry. From the experiments 

 I have made, I have satisfied myself that it 

 arrests, equally, vinous and putrid fermenta- 

 tion, and that in close vessels it may be used 

 for preserving both animal and vegetable 

 substances." 



Further information on this very important 

 and interesting subject may be had by refer- 

 ence to pages 27, 60, 77, 152 and 250 of the 

 third volume of the Farmers' Cabinet, to 

 which the reader is referred. 



The difficulties with the lime kiln, detailed 

 in the latter part of the esaay, have occurred 

 in the lime burning districts of Pennsylvania, 

 and they arise mainly from building the kiln 

 by plausible theory, instead of referring to 

 experience. The kiln is too high (22 feet) 

 in proportion to the diameter on the top; it 

 should be contracted but very little at the 

 top, otherwise it will choak ; and when the 

 waiste is much wider than the top, towards 

 the latter part of the burning the stone settles 

 down and leaves an opening around it, so 

 that the fire passes on the side of the kiln 

 instead of through the lime, and leaves it im- 

 perfectly burnt. In the lime-burning district 

 of Plymouth, Pennsylvania, fourteen miles 

 from Philadelphia, from whence comes the 

 principal supply of the city, the kilns burn 

 from 1500 to 2000 bushels at a time, and are 

 forty-eight hours in blast; which is twenty- 

 four hours less time than the Maryland kilns 

 are stated to be in burning, from which it is 

 inferred that there is something wrong in 

 the construction of the kilns or in their man- 

 agement, that ought to be rectified ; besides 

 which, there must be a great waste of fuelj 

 used in the process, where it is so long pro-i 

 crastinated. This is a subject well worthy! 

 of close examination, as in proportion to the 

 cheapness of lime will be the extent of its 

 application to the soil, 



Agricol.v. 



March 26, 1810. 



Men are so dependant on one another, and 

 the vicissitudes of fortune are so great, that it 

 should make people cautious whom they of- 

 fend, as accident may lay them under a ne- 

 cessity, at some future time, of applying to 

 those very persons for their friendship and 

 assistance. 



For tlie Farmers' Cabinet. 

 Mortar for Plastering. 



Communicated to tlie Pliilada. Agricultural Society. 

 BY JOSEPH CLOUD. 



As hard, durable and adhesive mortar or 

 plaster, is of such importance in the arts, 

 perhaps a few hints on that subject may be 

 useful in calling the attention of those who 

 have the direction of its preparation, and 

 serve to aid them in bringing the process to 

 a higher state of perfectioq than that in com- 

 mon use. Probably, the object desired can 

 only be obtained by proper care in the selec- 

 tion and perfection of the materials of which 

 it is composed. The substances necessary 

 for the composition of hard, durable and ad- 

 hesive mortar or plaster for building walls, 

 or covering the exterior of buildings, appear 

 to be pure silicious sand, and pure, fresh- 

 slacked lime (hydrate of lime.) The sand 

 should be tolerably fine, with the surface as 

 rough and angular as possible — that used by 

 the stone-cutters, (commonly called stone- 

 cutter's sand,) answers very well. The sand 

 should, in all cases, preparatory to its admix- 

 ture with the hydrate of lime, be perfectly 

 freed from earthy and all other impurities, 

 by washing with water. The hydrate of 

 lime should be prepared from pure, fresh, 

 wood-burnt lime, which after being slacked, 

 must be mixed with water until it forms what 

 is usually called milk or cream of lime, then ^ 

 passed through a fine sieve for the purpose 

 of freeing it from unslacked particles and im- 

 purities. At this stage of the operation, the 

 sand and lime are to be mixed together in 

 such proportions as to form a compound con- 

 sisting of nine parts sand and one part lime, 

 with the addition of as much water as may be 

 required to reduce the mass to a plastic state 

 of such consistence as may be proper for ap- 

 plication. As much of the perfection of the 

 mortar will depend on the mixture, due at- 

 tention should be paid to the complete incor- 

 poration, so that no tvvb particles of sand shall 

 exist without having the space or interstices 

 between them completely filled with hydrate 

 of lime. From the moment that lime is 

 slacked it acquires a strong affinity for car- 

 bonic acid, and a union is formed such as 

 existed in the limestone before burning; 

 consequently, mortar is obtained possessing 

 nearly the hardness o? flints, with the dura- 

 bilitv of silicious sand and marble, both of 

 which are impervious to, and insoluble in wa- 

 ter, and equally unaffected by the influence 

 of the atmosphere. 



The spaces between the particles of sand 

 having been completely filled by the hydrate 

 of lime in the effectual mixture of the ma- 

 terials forming the mortnr, the subsequent 

 uaion of the lime with carbonic acid, and tlie 



