Question: You made reference to handling "sacred linens and sacred vessels." Just what are these things and who may handle them?
Answer: The "sacred linens" are those cloths of linen or hemp that normally come into contact with the Blessed Sacrament. These include the purificator (an approximately 12" x 18" oblong linen napkin the priest uses to wipe the chalice and his lips), the pall (a stiffened piece of linen, perhaps six inches square, used to cover the chalice), and the corporal (about eighteen inches square, placed under the chalice or any other vessel containing the Blessed Sacrament). The corporal and pall should be blessed by the Bishop, or by a priest delegated by him. After having been used, they must be washed by a priest, deacon, or subdeacon before they may be handled by a lay person entrusted to washing and ironing them.1 If they are accidentally stained by the Precious Blood, they are washed three times.2 These washings by a major cleric are to ensure that particles of the Blessed Sacrament possibly clinging to the linens are properly disposed of in the sacrarium (a sacristy sink, piped into the earth) so that they cannot be accidentally trodden upon. Only after the washing(s) by the cleric will the linens be turned over for conventional laundering.
When starched and ironed, the purificator is folded in thirds along its longer dimension, and then in half in the other direction. The corporal is stiffened with a plastic insert if it is not made of several thickness of linen that can be stiffened with laundry starch. The corporal folds in thirds along both directions, in such a way that the section on which the Blessed Sacrament will sit is the innermost surface.
The "sacred vessels" are the containers used to hold the Blessed Sacrament during Mass, reservation in the tabernacle, and exposition. The chalice is a cup -- silver or gold if possible, but always gold plated in its interior -- to hold the Precious Blood. Normally, it consists of a more or less conical cup, a node where it is grasped, and a relatively massive and wide base. This construction is intended to keep it from tipping, either in the celebrant's hand or on the altar. The paten is a dish made of the same material as the chalice, at least gold plated on its upper surface. It should be of the proper size to nest on top of the chalice with a purificator in between the two. The edge of the paten must be relatively thin to allow its use in gathering up fragments of the Blessed Sacrament. The paten holds the large host for the priest, and if the number of communicants is small, it may be used to carry the Hosts for distribution. The chalice and paten must be consecrated by the ordinary.3 Once consecrated, the chalice and paten should be handled only by a cleric or a designated sacristan.4
The ciborium resembles the chalice in material and construction, although the cup is usually more cylindrical and must be fitted with a snug fitting cover. A ciborium holds small Hosts for the Holy Communion of the people. Covered and veiled it is the vessel for reservation within the tabernacle. The ciborium must be blessed.
A pyx is a small metallic container, about the size and shape of a pocket watch, with a gold interior, used to carry four or five Hosts for the Communion of the sick. It is blessed with the same blessing as the ciborium, and sometimes the word "pyx" is used interchangeably with "ciborium." A large pyx, able to contain many Hosts, may be used by priests taking Communion to a large number of people, for example, in a hospital or rest home.
The luna and monstrance are used for exposition of the Sacred Host. The luna usually consists of two pieces of circular glass, rimmed and hinged together so as to contain the Host. The monstrance is a stand that holds the luna during exposition. Monstrances vary considerably in size and shape, but are always designed so that the Blessed Sacrament is clearly visible. When placed in the tabernacle the luna is veiled or placed in a box called a custodial.
It goes without saying that, since the sacred vessels and linens come into contact with the Body and Blood of Christ, they must be kept scrupulously clean and in good repair.