ALABASTER. The general modes of working Alabaster with saws, chisels, files, and turning tools, as regards its configuration, are described in pages 164-5 of the first volume, but this substance is polished quite differently by the sculptor in chiselled or carved works, by the marble worker in turned works, and by the lapidary in small objects of bijouterie and vertu; it is therefore proposed briefly to describe these three several modes. 1. - Alabaster. - Chiselled or Sculptured Works. The dull or dead parts of sculpture, after having been carved with chisels, as more fully described under the head marble, are, 1st, smoothed with bent rasps and files, known as rifflers, and, 2ndly, are afterwards scraped with a triangular scraper. 3rdly, they are additionally smoothed with fish skin or glass paper, and, 4thly, with Dutch rush used with water.
In some few instances carved works are polished, or else the ground alone from which the figures are relieved is polished by way of contrast, in such cases after the four previous stages, the parts to be polished are wrought with the end of a stick of deal or other soft wood, supplied with Trent sand and water, and used as a pencil or brush with small circular strokes, and afterwards with a stick and putty powder with water, just the same as in corresponding works of marble, which are fully treated under that head in this Catalogue. 2. - Alabaster. - Turned and Polished Works. Mr. Hall of Derby has kindly furnished the author with the following outline of his usual practice. "When the article is finished with the turning tool, take, 1st, a piece of very fine soft sandstone, (found in Derbyshire in thin beds in the red marl formation,) and apply it with water to the work, whilst it is in quick revolution moving the stone all over until there is worked up a body of mud; 2ndly, take a wet rag and work this sludge well on the alabaster, then wash the work clean; and 3rdly, apply a rag charged with putty powder and water, until there is a gloss upon the work. 4thly and lastly, apply another rag charged with a mixture of putty powder, and soap and water, for a short time and wipe the alabaster dry which completes the polish." 3. - Alabaster as Treated by the Lapidary. Alabaster is far less frequently wrought by the lapidary than the sculptor, but as it is treated by the former in a manner somewhat different from the harder stones, it is made one of the three general examples of the lapidary's art, introduced into this catalogue, namely, the working of Alabaster; the working of Carnelian; and the working of Sapphire; which substances differ greatly in hardness. To these three descriptions are appended lists of the principal stones and other substances that are similarly treated, by Mr. Ward and other lapidaries, whom the author has consulted. In the Chapter on Lapidary Work these outlines will be filled up, and the general practice of this curious and interesting art will be considered somewhat more at length.
In working Alabaster to the required forms the lapidary first employs as usual the slitting mill, which is a thin plate of iron fixed on a vertical spindle, and made to revolve with moderate velocity, the edge of the sheer is charged with diamond powder, and lubricated with the Oil of Brick. This instrument which may be considered as the circular saw for small stones, is used with light pressure and plenty of brick oil.
Secondly the alabaster is roughed, or roughly ground on what the lapidary terms a roughing or lead mill, namely a flat circular plate of lead, fixed on a spindle similar to that of the sheer, the millor lap therefore travels in a horizontal plane, and is abundantly supplied with coarse emery and water by means of a brush. The stone is moved to and from the center of the rapidly revolving lap, until all the marks from the slitting mill are removed, and the stone is reduced to a flat surface.
Thirdly the alabaster is smoothed on the same lead mill with flour emery, but prior to smoothing the stone, the grains of the coarse emery previously used, and that remain on the lap, are rubbed down fine with a smooth lump of emery stone. It would apparently be a better practice to use two different laps, and together with them emery of two different sizes; as in the first place, the operation of smoothing the mill, is tedious, it also tends to wear away the lap towards the edge, thus degenerating the plane or flat surface into an irregularly coned surface, with which it is impossible to grind works accurately flat; and moreover if any coarse grains of emery are left in the lap, they greatly retard the smoothing, and consequently the polishing also. Indeed it will be found a most erroneous practice, to hurry over any one process with the intention of making up for it in the next, for as each stage of the work requires successively finer polishing powders, the various steps should be continued the proportional times, or ultimate success will be more tediously, if at all attained.
As it is difficult to polish alabaster and substances equally soft on the inelastic lead lap with rottenstone, (the means usually employed for harder stones,) the following is the course ordinarily followed. After the roughing mill has been used, the stone is smoothed on a wood mill or a disk of mahogany used with flour emery and water; on account of the greater elasticity of the wood mill, and the slight roughness of its face from the rubbing up of the fibres, it acts more quickly and satisfactorily than the metal tool.
Fourthly the earlier stage of the polishing is accomplished on a list mill with pumice-stone and water, but as the list which is wound on spirally is very elastic, flat works must be lightly applied, or they will sink into the soft face of the list mill and become rounded at the edges.
Fifthly the polishing is completed on a leather lap, or a thick piece of buff leather pasted securely on a wooden disk, and supplied with fine putty powder and water. Sometimes indeed the naked hand, and a little moistened putty powder are finally used for the last polish.
These several mills or laps are more particularly described under the article Wheels in this Catalogue.
The following substances are worked by the lapidary in nearly or exactly the same manner as Alabaster, and descriptive articles are severally introduced in the Catalogue upon these particular substances, pointing out also any peculiarities of method pursued either by the lapidary or other artizan, as the case may be, in working them.
(Substances treated by the Lapidary like Alabaster.)
4. - Cleaning Alabaster. - Ornamental works in alabaster that have become soiled are sometimes cleaned in the following simple manner: - The object is first immersed in plain spring water for four or five days, the water is then changed and a small quantity of lime is added, the alabaster is allowed to remain in this solution for a further period of four or five days, after which it is only necessary to thoroughly rinse the object, which is allowed to dry gradually in the open air, and the process of cleaning is completed. Should the alabaster have been very much soiled, a single course of the above treatment may fail to restore the original whiteness; in this case the process is repeated, and in extreme instances a third application is sometimes necessary. Earthenware pans are the most suitable vessels to be employed, as wooden tubs, especially those of oak, are almost certain to stain the alabaster.
Objects that consist of several pieces will be separated by the above process; they are, therefore, lastly, reunited with plaster of Paris, all the parts to which the plaster is to be applied being first moistened with water to ensure the adhesion of the plaster.
In the original working and finishing of the alabaster, all the pores or grain of the stone become filled with the fine powder produced in polishing, and which gives the alabaster a more compact surface than it would otherwise present. This powder is removed by the above treatment, and the alabaster then exhibits its natural granular and sparkling appearance: should this be objected to, the polish may be renewed by the employment of putty powder, applied upon a rag or stick as described in article 1.