What is rosin?
Rosin is a solvent-free cannabis extract. It is extracted through the skillfully balanced application of temperature, pressure and time. Different consistencies (e.g. budder or shatter) can be achieved through applying more or less of these three factors. The latest trend is live rosin, which is made from fresh-frozen, dehydrated flower of the highest quality.  The labor and time involved in manufacturing live rosin makes it a very expensive high, but the purest available.

How does a rosin press work?
Essentially a rosin press is anything that uses heat and pressure to extract terpenes and cannabinoids. Typically, it has two rectangular hot plates, between which the starting material (flower, kief, trim, etc.) is heated and pressed. Between the plates and the cannabis there is also usually either waxless parchment paper or a filter bag.
The main types of press are manual, hydraulic, pneumatic, electric and hybrid. Each uses a different mechanism to apply the pressure. You’ll also find DIY kits that will allow you to transform a regular shop press into a rosin press. The main difference between the types of press has to do with how pressure is applied.  Manual rosin press “squish” the plant matter with a clamp or screw mechanism, hydraulic and pneumatic use a liquid hydraulic pump or an air pump as the source of pressure and the electric press uses a motor to apply pressure. There are tricks to using any of these presses, principally applying the right amount of pressure and heat to the right amount of plant material.
What do I need to consider when buying a rosin press?
First, consider your available workspace:
If noise is going to be a problem, avoid pneumatic presses
If space is limited, pay careful attention to the unit’s dimensions
Where are you going to put the press? Will it be able to support the weight?
Will you often need to move the press or take it elsewhere?
Next, think about how much starting material you’ll need to process, what kind and how often:
Is manual operation going to become tiring or too time consuming? Consider a pneumatic or electric press.
Is the press versatile enough to handle different kinds of starting material well? The more adjustable the pressure and temperature, the more likely you’ll get good results with everything from trim to hash to flower
Finally, what end product are you looking for?
Some presses allow much finer control over heating and pressure than others, which allows you to achieve a wider range of rosin consistencies. If you like to experiment and perfect, bear that in mind