2. Pillow rests
In some Southern countries there are national traditions of lace making without rests. Lace makers sit on a carpet or a mate.
Lace makers of European school plate sitting on a chair. On this reason a pillow with pricked pattern is to be lifted at 24-36 inches (60-90 cm) above a floor. A table or a special rest is needed to fix a pillow at the mentioned level.
Due to a rest the bolster takes some position in the Cartesian coordinate system XYZ. Let us suppose that Cartesian axes OX and OY are on the horizontal plane and placed along the axes of the bolster symmetry; the axe OZ goes through the centre of its gravity (Fig.2.1).
Four parameters of the vector A describe the bolster position:
- h – height of the center of gravity above horizontal plane;
- azimuth ? – an angle of the bolster turning around the axe ОZ;
- elevation ? – an angle of the bolster inclining to the plane XOY;
- heel ? – an angle of the bolster turning around its longitudinal axe.
The rest is to allow angle controlling the bolster next way:
- unlimited azimuth turning, i.e. 0 to 360 grades;
- elevation inclining 0 to 30-40 grades;
- heel turning on ± 45 grades.
These are conditions of coupling lace making.
During plating the center of bolster gravity stays unmovable at the height that is choosen according to the bolster diameter, lace maker’s antropology and the chair height. The bolster must stay unmovable despite of any thread tension. On the other hand it must be turned easily when lace maker goes to the next pattern fragment. Hence two contradictory conditions are to be satisfacted:
- cotrollability when the bolster position is being changed;
- hard bolster fixation when lace is being plated.
Great number of bolster rests arose to fulfil both demands. All known rests can be gathered into three groups:
- rests on the horizontal platform;
- retst on the inclined platform;
- rests with the ball hinge.
These groups are listed here in the order of their historical evolution. The first group rests are the most ancient ones and are being used up today. The rests with the inclined platform are known since the 19th century in Germany. The rests with the ball hinge are used by russian lace makers in Vyatka since the second half of the 20th century.