During the seventeenth and eighteenth Centuries there were many attempts to reproduce in Europe the Chinese porcelain which was then so popular and profitable an import, and the products of these porcelain manufactories are familiar to most lovers of antiques. Far less familiar are the attempts to counterfeit porcelain by the use of opaque white glass with brilliant enameled decoration.
Regarded as something of a hybrid, this material has been misunderstood alike by those who find the supreme beauty of glass in the freezing to crystalline immobility of a molten substance in the moment of manipulation, and by those to whom porcelain is sufficient unto itself. Yet porcelain and glass are not so much dissimilar in substance as differently worked. The great French scientist Reaumur, indeed, attempted to solve the problem of making porcelain by devitrifying glass; but this proved a wholly uneconomic approach, and glassmakers in France and Germany, as well as in England, were content to copy in opaque white glass the outward appearance of the coveted porcelain. The comparison with porcelain is made quite explicit in at least one contemporary advertisement: "At the Round Glass House on George's Hill, near Mary's Lane, Dublin . . . jars and bakers [beakers] for mock china." (Faulkner's Dublin Journal, January 1752.)
The material itself presented little or no difficulty. Opaque white glass in thread form had been an essential component of much of the Venetian glass of the sixteenth and seventeenth centuries. The necessary technical information was widely disseminated on the Continent, both by means of Venetian-manned glasshouses there and, on the theoretical plane, as a result of the publication of Antonio Neri's ‘L'Arte Vetraria’ in 1612. This famous book, which was repeated in many editions and translated into many languages from the seventeenth century on, contained two recipes for milk-white glass (Chapters LIV and LV). Both were based on the use of tin oxide as an opacifier, and reflect Venetian practice. No doubt the first vessels of opaque white glass of which we know in England were made of this - the capped canisters, obviously following Chinese porcelain in shape, which the London glass-seller, John Greene, ordered by the dozen about 1668 from the Venetian glassmaker Allesio Morelli. Unfortunately, none of these appears to have survived.
The early years of the eighteenth century are less well documented, and it may well be that the great prestige of English clear lead glass at this date kept the makers too busily engaged in this line to make glass imitations of other materials. The next evidence dates from 1731/2 and comes, curiously enough, from America. In the ‘New England Journal’ of 24 January (quoted by W. A. Thorpe in ‘English Glass’), Mrs. Abbott, of Boston, advertised among other recent imports from England "fine white Glass Japann'd." There is always confusion at this date concerning the word "white," which may mean no more than "colorless"; but in this context the word "Japann'd" (i.e., painted) would seem to indicate the opaque white material, which "was (at a later date, at least) more commonly painted than ordinary clear glass.
In 1743 we have our first notice of opaque white glass from a particular glasshouse. The Countess of Hertford, writing to her son, says: "They have made a great improvement in Southwark upon the manufacture of glass, and brought it so nearly to resemble old white china, that when it is placed upon a cabinet at a convenient distance it would not easily be distinguished by an indifferent judge. They make jars, beakers, flower-pots, sauce-boats, salt-cellars, and milk-pots of it, which look extremely pretty." In a subsequent letter she returns to this topic with the remark: "The difference between old china and the glassware is not in the transparency . . . but from a bluish cast in the white, which is only observable when placed by real china."
Mention of a bluish cast in the glass suggests that this was one of the "fiery opals," showing a red glow by transmitted light. A good deal of nonsense has been written about the difference between the "solid creamy-white Bristol" enamel-glass and the "milk-and-water" and "fiery opals," the former supposedly made opaque by means of tin oxide, the latter by arsenic or bone ash. In fact, the opacity of enamel-glass may be produced in two ways: (a) either by particles of a substance which have not been in solution in the glass, because the heat was insufficient or because the substance was too abundant or its particle size too coarse; or (b) by the crystallizing out of opal materials which had been in solution in the melt.
Of the former category are tin oxide and bone ash; the particles introduced even as very finely ground powders will be large compared with the wavelength of light and will give white reflection with no appreciable "scattering" of blue light. If the particles are very numerous they will give a dense opaque material; if not, the opal will have a watery appearance.
Of the second category are tin oxide and bone ash when they have been in complete solution in the melt, and also arsenic. During the original cooling of the melt the opal material will begin to crystallize out as an extremely large number of minute crystals; these will grow individually and may form aggregates if they grow large enough to come into mutual contact, or under certain conditions some of the larger crystals may grow at the expense of the small neighboring ones. If the crystals remain small but are very numerous, they will give an opaque white, which will show no "fire" unless the specimen is very thin. If the crystals are small but less numerous, they will give a milk-and-water white, with possibly a hint of blue when seen by reflected light; but a fiery opal when a thin specimen is looked through. With very small crystals fairly thinly dispersed the glass will be blue by reflected light and fiery when looked through, the intensity of the fire depending on the thickness of the specimen. If the amount of opal material is large and the crystals have developed to a comparatively large size, the effects will approach and may eventually be indistinguishable from those due to particles which have been introduced into the glass and have not completely dissolved. Without an extensive series of experiments, therefore, it would be rash to dogmatize on the opacifier used in a given glass merely on the strength of its opacity, its fire, or its milk-and-water quality. To say that Bristol enamel was dense and white and showed no fire merely on the basis of Professor Church's much-quoted analysis (first published by Hugh Owen in ‘Two Centuries of Ceramic Art in Bristol’, 1873) is open to grave objection. In the first place, the amount of tin oxide used ("Binoxide of Tin .86%") was more likely to produce a fiery opal than a dense enamel. In the second place, we do not know what glass Professor Church analyzed: it is stated to have been of "the Bristol enamel glass," but this is begging the question. The only recipe we know left by a Bristol man was Anthony Amatt's (also quoted by Owen), and that was for an arsenic enamel.
All three methods of opacifying glass mentioned above were known in England in the mid-eighteenth century, and are described by R. Dossie in his ‘Handmaid to the Arts’, published in 1758. The glass seen by the Countess of Hertford at Southwark, however, was almost certainly produced by the use of arsenic. Dossie refers to enamel made by this method "in a considerable manufactory near London," and in his second edition (1764), in the same context, to "a composition of paste of an opaque whiteness formed by arsenic . . . made at a considerable work near London in great quantities, and has not only been manufactured into a variety of different kinds of vessels, but, being very white and fusible with a moderate heat, has been much used as a white ground for enamel . . .". These two passages taken together must mean that the "manufactory" was a glass-house, making enamel-glass both for its own use and for sale to the makers of enameled metal goods, and was not an enamel factory like Battersea, as Mr. Thorpe suggested in his ‘History of English and Irish Glass’. That the glass-house was in fact that at Southwark seems confirmed in another passage in Dossie's second edition (I, p. 334, "Of common white glass as an enamel ground"): "The white glass made at Mr. Bowle's glass-house in Southwark is frequently used for the grounds of enamel dialplates, and other painted works. It is a glass rendered of an opaque whiteness by the admixture of a large proportion of arsenic." The "composition glass" stolen from Benjamin Bowles' warehouse in Stony Street, Southwark, in 1774 may well have been of this material (quoted by W. A. Thorpe in ‘English Glass’). However this may be, it seems certain that opaque white glass made by the arsenic process (not the bone ash, as suggested by Mr. Thorpe, ibid.) was being made by Bowles in Southwark from at the latest 1743 until at least 1764. The production of opaque white glass at a "considerable manufactory" which was clearly renowned for this specialty, for at least twenty-two years, cannot have been inconsiderable.
Why then do we not hear of "Southwark," but always of "Bristol," opaque white glass? The reason is certainly to be found in the tradition concerning one Michael Edkins, of Bristol. Michael Edkins is one of the few eighteenth-century ceramic artists about whom we know a certain number of details. His son dictated to his son a brief account of Edkins' life, and this grandson transmitted it to Hugh Owen, who incorporated it in his ‘Two Centuries of Ceramic Art in Bristol’. The gist of it is that Michael Edkins was apprenticed in Birmingham - where, incidentally, William Beilby, of the famous Newcastle family, was also apprenticed - but, his master dying, he came to Bristol before his apprenticeship was up. There he was employed as a delftware painter until the delftware industry declined, when he became a coach and general painter. He was also "exceedingly clever at ornamenting enamel and blue glass ware, then much in vogue, at which he had no equal." The statement of the son was coupled with a number of attributions made either by the grandson or by Owen. The whole question of these attributions has been debated before, but suffice it to say that a set of delftware plates (one is shown) with the initials E/MB (for Michael and Betty Edkins) and the date 1760 may be accepted as Edkins' work; but the attribution to him of several types of painted or gilt glass - palpably by different hands, if style counts for anything - should be viewed with the greatest skepticism. It becomes more than ever necessary to look for criteria by which it may be possible to re-assess and re-attribute English enameled opaque white glass.