Metal soprano clarinets were common in the early 20th century until plastic contraptions supplanted them; metal construction continues to be used for the bodies of a few contra alto and contrabass clarinets and the necks and bells of nearly all alto and bigger clarinets. Ivory was used for a few 18th century clarinets, but it tends to crack and doesn't keep its shape well. Buffet Crampon's Greenline clarinets are crafted from a composite of grenadilla wood powder and carbon fiber. Such clarinets are less littered with humidity and temperature changes than wooden gadgets but are heavier. Hard rubber, corresponding to ebonite, has been used for clarinets because the 1860s, even though few modern clarinets are made of it. Clarinet designers Alastair Hanson and Tom Ridenour are strong advocates of hard rubber. Hanson Clarinets of England manufactures clarinets using a grenadilla compound bolstered with ebonite, known as 'BTR' bithermal reinforced grenadilla. This cloth also is not affected by humidity, and the burden is an identical as that of a wooden clarinet. The reed is on the underside of the mouthpiece, urgent towards the player's lower lip, while the end teeth invariably touch the top of the mouthpiece some players roll the higher lip under the end teeth to form what is termed a 'double lip' embouchure. Adjustments in the power and shape of the embouchure change the tone and intonation tuning. It is not rare for clarinetists to employ how you can relieve the pressure on the higher teeth and inner lower lip by attaching pads to the top of the mouthpiece or placing brief padding on the front lower teeth, commonly from folded paper.