I found this: "It can takes some time to get amber dissolved in acetone but it is a starting point."..."Put some pieces of amber into acetone and leave it for several weeks. After a month, the solution turns yellowish, then you add some petroleum naphtha and leave it for  another couple of weeks or more... at the end, most of amber dissolves or at least, it has a chewing gum consistency".

Some internauts suggest adding some caustic potash alcoholic solution to a acetone-naphtha-crushed amber blend and putting it into a ultrasonic bath chamber to speed up the process...  I would avoid volatile gases formation under pressure... that can form a mix of explosives gases...

Also, I found this in the net:

"I got this from a book entitled "Violin Varnish and How To Make It" by G. Foucher published in 1911. he wrote this about amber.....

"In its natural state it is not soluble in alcohol nor essence of turpentine nor essential oils. It can, however, be dissolved by the following process. Place some in a clean earthenware vessel and heat it gradually, when melted pour on to a marble slab, when it becomes hard again reduce it to powder. It can then be readily dissolved in spirit, essence of turpentine and also in all the oils extracted by the distillation of tar."..."

I would recommend to crush the raw amber by grinding it to powder in a coffee grinding machine for example,  and then poor it into linseed oil or turpentine and then heating this blend gradually, really slowly and carefully, avoiding thus decomposition by heat. The same principle is used for lowering the melting point of metal alloys.

Interesting info can be found here:

http://www.madehow.com/Volume-7/Amber.html

http://www.madehow.com/Volume-7/Amber.html

Since 1881 (pioneered by the Austria-Hungary company Stantien & Becker) small chips of Baltic amber that were too small for use in the jewellery trade have been softened (but not melted) to enable them to be pressed into larger blocks known as “ambroid” (sometimes “amberoid”). Those blocks were then carved to produce beads, buttons, brooches, hair ornaments and other decorative items.

There were three main methods in use, named after their inventors. The Spiller method required amber fragments to be placed in a cubical steel mould with a tightly fitting top plate. The entire assembly was heated gradually by immersion in hot liquid paraffin or glycerine and then the top plate subjected to a pressure of 400 - 500 kg/cm2 to press the fragments into a mass that solidified into a block.

The Trebitsch method used a cylindrical mould having two sections divided by a barrier wall with small holes in it. The mould was heated to soften amber fragments placed in the lower chamber and it was then squeezed through the holes into the upper chamber via a piston to become a homogeneous mass. Much higher pressure was needed for this – above 3,000 kg/cm2 but it produced a better result.

Ernst Simon then patented a process in 1903 for directly pressing heat-softened amber into detailed moulds to reduce the wastage arising from carving. More intricate items (such as cigarette holders and pipe mouthpieces) could then be cheaply mass-produced - only requiring drilling and polishing to finish them.

Modified and improved versions of these processes are still used today, generally using superheated steam in an autoclave as the heat source. The best results are achieved with temperatures controlled at above 204 degrees Celcius and below 220 degrees, with pressures between 2,400 and 2,700 kg/cm2. It is essential that the amber is thoroughly cleaned of debris and weathering crust and that the process is performed in an airtight oxygen-free environment (vacuum or inert gas) to prevent oxidative darkening and subsequent deterioration.

As already stated, amber doesn’t melt in the true sense of the word, but it does undergo a transition above temperatures between about 250 - 350 degrees (depending on age, origin and composition), at which point it is actually decomposing.

Essentially, the same processes are used today for much of the so-called “amber” jewellery sold cheaply in gift shops (although it is contrary to International Amber Association rules to call it amber), often with the added refinement of dyes to improve or change the colour.

There are other methods in modern use, developed in the late 1950’s. Granulated amber (mechanically crushed) is heated to temperatures between 150 -200 degrees Celcius and pressed between 200 – 300 kg/cm2 without the benefit of vacuum. That method yields a dark red colour, with low clarity and an obvious “crazed” appearance of a non-uniform nature. The colour and clarity can be improved somewhat by moving closer to 140 degrees (the lower limit of softening), but you then need more pressure. Given enough pressure you can even force small amber granules to bond together at temperatures below the softening point.

https://www.gia.edu/gems-gemology/summer-2014-wang-heat-treatment-of-baltic-amber

I follow the method of Ronald Maldonado Rodriguez, to crush the raw amber by grinding it to powder in a coffee grinding machine for example,  and then poor it into linseed oil or turpentine and then heating this blend gradually, really slowly and carefully, avoiding thus decomposition by heat.

I  haven't the slightest idea about the problem. Sorry Marin.

Jean-Philippe