A. H. Lees 



359 



These conditions formed a solid coat of calcium carbonate not only 

 on the surface but in the lower layers as well, thus making an exceedingly 

 hard and smooth coating. Unfortunately these conditions are im- 

 possible to obtain out of doors as drying takes place quickly and only 

 small quantities of carbon dioxide are present. 



None of the additions made to the lime improved the coat, while 

 most of them made it distinctly worse. 



To test whether carbonating before appHcation improved the mixture, 

 carbon dioxide was passed into a beakerful. When poured on a glass 

 shde and dried a brittle coating was obtained which is quite useless. 



Field experiments. 



These were first arranged on upright flat-sided posts. The results 

 were subsequently found unreliable. 



When sprayed on twigs of a tree the coating is subject to violent 

 movings of bending caused by the wind, which are absent in the case 

 of an upright post. It was found that such bendings of the dried 

 coat was largely instrumental in causing flaking. The trial lasted 

 ten days in December during which much rain was experienced. 



-^ Li 



a) <S rt 0) 



§ I* .5 o .g ^ a fl I %% 1o 



(1) 20 2 — — — — — — 100 Moderate coating Largely washed 



away 



(2) — — 8 ^ J — — — 10 Moderate coating Showed slight signs 



of thinning 



(3) — 8 1 J ^ — — 10 Moderate coating Showed very little 



signs of thinning 



(4) 14 7 1 1 J — — 80 Moderate coating Very good and thick 



coating 



(5) 2 — — — — — riT TO 10 Thinned down be- Very poor 



fore applying as 

 too thick to go 

 through nozzle 



iQ\ 2 — — — i^o Iff 10 Do. Do. Thinned in places 



(7) 2 — — — — — • A tV 10 Unstrained and Thinned in places 



thrown on and flaked 



/g) 2 — — — Tff Yu 10 Do. Do. Thinned rather more 



than (6) 



(9) 2 — — — — — tV iV 10 Do. Do. Too thin when ap- 



plied 



(10) 1| — — — — 1^ tV 10 Strained, sprayed, Showed very little 



etc. signs of wear 



(11) 1 — — — TT 57 10 Ditto but too thin Far too thin 



(12) 1^ — — — ,% tV 10 Appeared most Thinned rather 



suitable badlv 



