The Recessing Process Illustrated in Stages on a Flat Surface
Recessing for enamel is time consuming but produces results that can't be equalled by other methods. Edges are clean and absolutely geometrically true. Corners are sharp with no radius. (Acute angles are trimmed by hand.) Recessed surfaces are prepared to a very high standard, very few steps away from a mirror finish minus the polish, by scraping, stoning and abrading with fine pumice so that the reflections from the engine turning, which is dependent on surface quality because of the guide controlling depth of cut, will be absolutely clean. This was particularly important in this example with sunray straight lines.
The blank dial stuck to a wooden block with wax. You can't see the marking out because it is too fine.
After very careful marking out on the straight line machine the edges of each recess are sunk. Positioning of the edge of the tool exactly in the middle of a mark of less than 0.01mm width requires a binocular microscope attached to the machine and accurate manipulation of controls.
The rough recesses cut away. At this stage the only accurate thing is the edges. The bottom of each recess is just a planed surface, OK if for opaque enamel but we are using translucent here.
The depth of the recess for enamelling is usually about 0.35mm before the pattern is cut in the bottom. On small 18ct gold work this would require a total guage before recessing of 0.75mm minimum for stability. Larger pieces require heavier guages or strengthening with wires, and possibly counter enamel also. For silver, substantially heavier guages are required. For details on individual jobs we would consult, or recommend that you consult, the enameller as determining appropriate guages for enamel is outside the scope of this reference work.
The high points, ridges and furrows produced during rough sinking are carefully scraped by hand using a selection of purpose made scraping tools to produce a level surface. This process is extremely critical and the scraper must be in absolutely the right condition (surprisingly edge quality is not what you would expect - too clean and it chatters, but it must be very sharp indeed). Scraping is a whole art in itself and requires great patience to produce really good results. Do it wrong and you make the surface worse!
After Stoning with Water of Ayr and cleaning up with fine pumice the surface of each recess should be good enough that if you polished it, it would produce a mirror finish. Any undulations at this stage will show in the engine turning if the pattern has straight lines in it.
Taking the first sunray cut. A guide is in use but the surface has been set up so well that if the depth stop were used instead the depth of cut wouldn't vary. This is very important as the depth stop will be required for the final cut.
Cutting the lines in the prepared recesses.
Ready for the final trim lines around the edges of the recesses.
A recessed enamelled clock about 200mm or so high. This was many hours work, particularly recessing around the roman numerals.
Recessing on two levels. This piece was made by the best goldsmith in the world, though you would have to examine it properly to see this. In times past, before he became a director of Grand Masters Designs Ltd, he used to supply a number of our Bond Street customers and work would appear in our London workshop with brief instructions from the customer. Only the quality of the work would tell us who made it and that we should make a discreet call and discuss the job in more detail! We have found this identification easy even though the design style of the piece varied from one firm to another because the order of excellence of this genius's work over all the others past and present is so large.