< WAX RETOUCHING
INSPECTING THE WAX PATTERN
Just like the original construction of the master pattern, a careful inspection at the foundry of the wax pattern is one of the critical points of the artist’s involvement in the lost wax casting process. Although the original master pattern functioned as a ‘template’ for the cast, it is the wax pattern alone which forms the actual impression of the sculpture in the investment mould. Differences between the master pattern and the wax pattern will therefore be evident in the metal cast and any errors will need making good during the metalworking stages.
Defects in the wax pattern can occur for any number of reasons, typically, a minor mis-registration of the reproduction mould, or a surface fault missed when wax chasing. Whilst art foundries generally take great care to produce high quality wax patterns, it is unwise for any artist to simply assume that their wax pattern will be exactly as desired unless they have an established working relationship with the founder. Errors will be more likely to arise at this stage of the casting process if the waxworker does not have an intact master pattern available for reference, underlining the importance of making good quality patterns in the studio.
It is desirable, if not essential, for the sculptor to either personally approve the final retouching of their wax pattern, or else complete this work themselves. Exceptions are sometimes made where multiples are being produced, this is common in cast jewellery work – though even here an individual sample is usually first provided for the designer’s inspection. Some artists have an exceptionally good understanding with the foundry waxworker, and may pass the approval of repeat work to the founder’s discretion. However, it is advisable to personally check all the waxes produced in the foundry.
It is generally accepted that instructing a foundry to proceed with the casting of a work without any prior inspection and approval of the wax pattern, limits the artist’s ability to reject a metal cast showing evedence of waxworking faults (even those of the foundry’s making). With this in mind, passing over the opportunity to inspect a wax pattern before casting proceeds, is a decision that should be very carefully considered. Adequate time for an inspection of the wax pattern should always be allowed for when planning a casting project, and this may factor in the selection of an appropriate foundry – especially if a the premises are located some distance from the sculptor’s studio.
As a rule, the founder will contact the artist and arrange a mutually convenient time to visit and view the wax pattern. It is advisable to respond promptly, as wax patterns are prone to damage and are not well suited to long term storage. It is not unusual at this stage for a wax pattern to have a variety of temporary supports attached, or for it to be already cut into convenient sections for casting, complete with patches removed and so on. Those sculptors unfamiliar with the founding process should not be surprised to see their wax pattern appearing somewhat differently than perhaps imagined. It can be visually challenging to see past any superficial distractions when working a foundry prepared wax, but given a little time to adjust, any initial difficulties can normally be quickly overcome.
Foundries usually have a skilled waxworker to hand who will be made available to assist an artist if wanted. For those artists who do not possess specialist waxworking tools, most foundry workshops will have a selection of tools available for their client’s use – it is a usual courtesy to take care of any loaned tools and to return them cleaned for the next user.
A common mistake made by artists and designers with limited foundry experience, is to overwork a prepared wax pattern. The extensive reworking of a wax pattern should be unnecessary provided a well considered master pattern was constructed in the first place and the founder took adequate care over the preparation of the wax copy. A major re-working of a wax in the unfamiliar environment of a foundry workshop is not especially conducive to the production of fine casts, so it is far better at this stage to concentrate primarily on a ‘fine tuning’ of the work. Where a remodelling of the wax pattern is unavoidable, extreme care must be taken not to remove too much of the wax close to the underlying core.
Excessive removal of the wax’s wall thickness may later cause a mis-run, owing to the resulting air gap reduction arresting the flow of molten metal through the investment mould. Building up too much additional wax on the other hand creates an unevenness in the cast wall thickness, this can produce an overweight cast – in extreme cases the founder may even accidentally misjudge the quantity of metal required for the melt. This would lead to a ‘short-run’ in the investment mould and an incomplete metal cast.
As a rule, faults which are evident in the wax pattern, but not on the master pattern, are rectifiable by the founder at the founder’s expense – in exceptional circumstances correction may mean a remake of the wax pattern to the client’s satisfaction. Changes to the wax pattern that are a result of a rethink by the artist, or errors in the construction of the master pattern are not normally the founder’s responsibility. Engaging foundry personnel in an extensive reworking of a wax pattern under these circumstances can result in the sculptor paying a surcharge for additional labour costs.
COMMON WAX FAULTS >
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