Treatments Done On Amber

by Manisha G

raw-amberThe amber may be clear and transparent, when it is known as clear, or it may be slightly turbid owing to a number of contained gas bubbles and then resembling goose fat, and hence termed fatty. A variety containing a vast number of bubbles making the material quite cloudy is called bastard, while bony or osseous amber has the appearance of dried bone. The small pieces not of gem quality are treated by heat in order to produce succinic acid, amber oil and colophony, the letter being used for the preparation of varnish.

Small piece which are clear enough for gem use are pressed together under gentle heat in order to produce pieces of a size suitable for working – a true reconstruction. This pressed amber, or ambroid as it is called, was made by a process first carried out in Vienna; the small pieces of amber (which soften at about 180°C) are welded together under high pressure. Such pressed material may be identified by the margins of different clarity and by the elongation of the bubbles due to the flow under pressure. Cloudy material may be clarified to some extent by careful heating in rape seed oil (colza oil), which penetrates and enters the air spaces causing the cloudiness. This clarified amber, unless great care in taken in the operation, will often exhibit crack-like marks. These are known to the amber workers as ‘sun spangles’ and are possibly due to stresses set up in the amber, or release of such stresses. Staining, too, is carried out, sometimes to redden the yellowish-brown colour in order to simulate the so-called ‘aged’ colour of amber, or to produce other colours, particularly green. Amber is frequently heated to darken its colour by increasing the speed of surface oxidation.

Some of the information available on the basis of studies on pressed amber state that those ambers were nearly trans­parent and homogenous in appearance and no signs of glow were apparent in ordinary light. Under long-wave ultra-violet light, however, the samples showed a strong whitish fluo­rescence, and the shapes of what had previously been individual fragmented pieces could be seen. Further tests carried out by flotation in a suitable S.G. solutions showed the pressed amber to be slightly but appreciably lower in density than a number of natural pieces. Their SG, when determined by hydrostatic weighing, was 1.06 against the 1.08 figure which is normal for block amber.

Leave a Comment

Previous post:

Next post: