2.1 Cannabis resin

 2.1.1 The most common form of cannabis resin is of Moroccan/North African origin, also known as "soap-bar" with a THC content typically between 4 and 7%. The resin appears in the UK in compressed bars, normally 250g/9oz.

2.1.2 The second most common form of resin is of Asian origin, being darker in colour and of soft, pliable consistency. Mostly from Pakistan or Afghanistan, it often appears in 1kg blocks wrapped in red cellophane. THC contents typically 4% to 10%, may also contain perfume agents such as caryophylline.

 2.1.3 Other types of cannabis resin appear occasionally. Lebanese resin was the "Market Leader" in the 1980s but is now rarely seen. Occasionally more exotic Himalayan varieties, with THC contents in the region of 10%, appear in small quantities.

 2.1.4 In the Netherlands, coffee-shops supply a wide variety of cannabis resins and herbal cannabis, with prices linked to quality (i.e. lower qualities provide larger fixed-price "deals"). The Netherlands has also started producing resin from domestically-produced crops. I know of one instance in the UK where resin produced from exceptional plants has approached a THC content of 60%.

 2.1.5 The overall quality of imported cannabis and cannabis resin appears to have fallen in recent years, many users perceive cannabis resin as adulterated, and forensic analysis has discovered common contamination of resin of both major types with "caryophylline" a constituent of cloves, also used in the perfume industry.

 

2.2 Herbal Cannabis

 2.2.1 Until recently, most herbal cannabis in the UK was imported from Africa, the Far East and Caribbean, however home-produced cannabis may now represent the major source.

 2.2.2 Imported cannabis appears in compressed blocks normally bearing seeds, and would typically have a THC content of 3-8%. Such material frequently appears in poor condition with mould and decomposition present (accelerated if damp - a potential risk for immuno-compromised individuals).

 2.2.2 Home grown herbal cannabis falls into three basic categories. "Hemp" is the fibre-producing variety which can be cultivated under licence for industrial uses, and would normally produce a THC content of under 0.5% (although some long-established cultivars, and individual plants, may produce higher or lower THC contents), and a relatively high CBD:THC ratio.

 2.2.2 Until recent years, most domestically produced cannabis for drug content was derived from seeds in imported "deals". THC content would be from 1% to 8%, similar to imported cannabis.

 2.2.3 In the past decade, commercial seed developers based in the Netherlands have developed a number of cultivars (e.g. "Skunk", "Northern Lights" and many others) suited for indoor growth by virtue of short stature (internodal lengths), and early flowering. THC contents are increased by preventing pollination of female plants by males, leading to "sinsemilla" - development of extensive flowering tops. The THC contents of these varieties in ideal conditions vary considerably, from around 5% to 15%, with exceptional cases producing 20% THC. The cannabinoid spectrum of these plants also varies. I am not aware of any data available on the actual cannabinoid composition of different varieties, although CBD levels tend to be low or absent.

 2.2.4 The THC contents associated with "Skunk" cannabis should not be considered unusual, as similar potencies were reported from some imported material seized in the 1970s and 1980s. Furthermore, THC losses in storage and transportation can render imported cannabis significantly inferior to domestically-produced product.

 

2.3 Cannabis Oil

2.3.1 The legal position of liquid cannabis (also known as "hash oil") is currently the subject of legal argument. This dark, viscous, liquid is prepared from solvent extraction of cannabis plants, and contains a high level of THC (10%-70%).