The altar-linens are the corporal, pall, purificator, and finger- towels. The Blessed Sacrament and the vase containing It must always be placed on a corporal, which must be made of linen (Miss. Rom., Ritus celebr. tit. i, n. 1) or hemp (Cong. Sac. Rit., 15 .May, 1819) without any embellishment or embroidery. Corporals made of muslin (Cong. Sac. Rit., 15 March, 1664) or cotton (ibid., 15 May, 1819) are forbidden. The edges may be ornamented with fine lace, and a cross may be worked into it near the front edge. No cross is allowed in its centre (De Herdt, I, n. 167), which would necessarily give some difficulty when collecting the fragments. The rubrics do not prescribe its size. It must be spacious enough to hold the chalice and large host used by the priest, and also the ciborium containing the smaller hosts for the Communion of the laity. It should be a square, at least fifteen by fifteen inches, or an oblong, fourteen by eighteen inches. The corporal must be blessed by a bishop, or by a priest having the faculty to do so, before it may be used the first time. It is not blessed again after it is washed; use at the Holy Sacrifice does not constitute a blessing (Cong. Sac. Rit., 31 August, 1867). The form of the blessing is the "Benedictio corporalium" found in the Rituale Romanum (tit. viii, cap. xxii) which is not changed to the plural even if many corporals are blessed at the same time (Cong. Sac. Rit., 4 September, 1880). The corporal loses its blessing when no part of it is sufficiently large to hold the chalice and host together, and it is forbidden to use a torn or ripped corporal. When the corporal becomes unfit for use it should be destroyed by fire, and its ashes thrown into the sacrarium. After the corporal has been washed, bleached, and ironed it is folded into three equal parts, both in its length and in its width, i.e. the anterior part is folded over the middle; then the posterior part is turned down over the anterior part; after this the part at the priest's right is folded over the middle, and finally the part at the priest's left is folded over these. The corporal is placed in the burse in such a manner that the edge of the last fold is towards the opening of the burse. It is probable that the corporal was prescribed as early as the fourth century. Originally it was longer and wider than the one in use at present. It covered the whole table of the altar, and was looked upon as a fourth altar-cloth. About the eleventh century it began to be curtailed, and by degrees was reduced to its present size. The Carthusians use the corporal in its old form (Benedict XIV, De Sacrif. Missae, I, no. 31).
Originally the pall was not distinct from the corporal, because the latter was so large as to do away with the need of a distinct pall, and the posterior part of the corporal was so arranged that it could be easily drawn over the host and chalice. When the corporal was reduced to its present size the pall became a distinct cover of the chalice, and is called by Benedict XIV Corporale quo calix tegitur (ibid., no. 34). Although prescribed by the rubrics, theologians hold that its use does not bind sub gravi. It may be a single piece of linen or hemp, or it may consist of two pieces of linen or hemp, between which a piece of cardboard is inserted for the sake of stiffening it. The upper side may be ornamented with embroidery or painting in various colours, or covered with cloth of gold, silver, or silk of any colour except black (Cong. Sac. Rit., 17 July, 1894). It may be embellished with a cross or some other emblem. The nether piece must always be of plain white linen or hemp (ibid.) and be detachable for the purpose of washing it (ibid., 24 November, 1905). Since the pall was originally a part of the corporal, the blessing "Benedictio corporalium" is used without change in number or words when blessing one or more palls alone, or one or more palls with one or more corporals (ibid., 4 September, 1880). Like the corporal, it is blessed by a bishop, or by a priest who has faculties to do so. It should be large enough to cover the paten. If the pall is wanting, a folded corporal may be used in its stead.
The Purificator is a piece of pure white linen or hemp (Cong. Sac.. Rit., 23 July, 1878) used for cleansing the chalice. Its size is not prescribed by the rubrics. It is usually twelve to eighteen inches long, and nine or ten inches wide. It is folded in three layers so that when placed on the chalice beneath the paten its width is about three inches. A small cross may be worked in it at its centre to distinguish it from the little finger-towels used at the "Lavabo", although this is not prescribed. It is not blessed. It is also called the "Mundatory" or "Purificatory". The Greeks use a sponge instead of the linen purificator. Before soiled corporals, palls, and purificators are given to nuns or lay persons to be laundried, bleached, mended or ironed, they must be first washed, then rinsed twice by a person in sacred orders (Cong. Sac. Rit., 12 September, 1857). When preparing soiled corporals for the altar a little starch may be used to stiffen them and give them a smooth surface. The same may be done with the palls. The purificators are always prepared without starch.
Finger-towels, used at the "Lavabo" and after administering Holy Communion, may be made of any kind of material, preferably, however, of linen or hemp, and of any size.
- article from the Catholic Encyclopedia at www.newadvent.org