62 
Table IV. — Tests on Vulcanised Rubbers, prepared from “Block” 
containing Mineral Matter. 
Vulcanisation 
Tensile 
Elongation 
Elongation 
reference 
Mixing. 
strengths. 
at rupture 
under a strain 
number. 
in grms. 
when original = 1. 
of 1500 grms., 
58 
M 
4746 
9*9 
6*0 
54 
J 
39 I 5 
117 
6*i 
The addition of mineral matter has had the effect of increasing 
the tensile strength while reducing the elongation. This effect is 
quite general within certain limits, and further tests are being carried 
out in which we are investigating the influence of definite quantities 
of mineral matters on mixings containing plantation block on the one 
hand and hard cure Para on the other. 
Plantation Rubber by Figgis & Co. 
Messrs. S. Figgis and Co., in their annual review of the India- 
rubber market, give the following re plantation rubber, which we 
extract verbatim : — 
Manufacturers have shewn a decided preference for sheet, biscuit 
and crepe ; the latter should not be drawn out too thin or have visible 
air or steam bubbles in it, and some lots of thick crepe, nice strong 
rubber about ^ of an inch thick, were much appreciated and sold well. 
We think it has been profitable to planters to wash and clean the 
rubber thoroughly, and to prepare as large a proportion as possible of 
good colour — also not to send many qualities or very small lots. Block 
has not been in favour generally, and unless clean, resilient, hard quality 
can be sent, it may be better to ship as crepe. 
We report our recommendations of a year ago : — 
Pack it in good dry condition (excess of resin much objected to). 
Into strong cases of i cwt. to 2 cwt. each. No paper, fullers earth, 
etc., to be used. 
To keep different qualities and colours separate, and not to mix 
immature rubber with older; to send separately dirty barky pieces, 
and to wash out all the bark in crepe, block, and sheet. 
All fine qualities should be loose crepe, sheet, or biscuit — not run 
into a mass. 
To smoke the rubber when convenient, because “smoking” 
appears to increase its resiliency, but keep it as clear and yellow as 
possible. 
Smoked rubber appears to have greater resiliency and to be more 
suitable for many purposes than unsmoked. “Smoking” prevents the 
“proteins” in rubber from decomposition, and generally from 
“ tackiness.” All fine rubber from Para is smoked. 
