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SECTIONING PATTERNS
Master patterns may be sectioned (cut into smaller pieces), for a variety of reasons, the most common being to accommodate the casting process. All foundries ultimately have a limit to their metal pouring capacity, so any casting mould must be of a size and volume that permits a comfortable pour. Bear in mind here, that allowances must be made not only for the quantity of metal in the sculptor’s design itself, but also for the amount used to for the metal RUNNING SYSTEM, plus a certain amount of safe excess. As well as capacity, the founder may also be limited by the size of investment or sand mould they can comfortably handle and process. Carefully dividing the pattern can minimise the occurance of a MISRUN, improving the chances of successfully casting a complex or other challenging design.
There are no real hard and fast rules about sectioning patterns, though received wisdom dictates that as few divisions as possible are made. This may mean finding an alternative foundry if your usual founder does not have the facilities to cast a large artwork in a reasonable number of pieces. Undeniably, cutting disrupts a design, and excessive cutting increases the chance of error creeping in during re-assembly at the finishing stage.
Ideally, the sculptor will section their own work in the studio. Cutting in advance of delivery to the foundry offers several advantages. The artist retains control and can dictate the precise cut line, the artist can also construct interlocking joints for registration (the best known of these is the male/female type ROMAN JOINT), and later break down the pattern for easy storage and transportation. To section in the studio successfully, the sculptor will need to have both the appropriate patternmaking skills, and a good knowledge of their founder’s working methods and casting capacity. Sectioning decisions are usually made in close consultation with foundry technicians.
Most art foundry patterns are not sectioned by the artist, but by the founder themselves. There are several ways the founder can do this, according to the circumstances of the job in hand, and their preferred working methods.
The founder may elect to physically cut up the artist’s pattern into smaller sections. This is a practical solution, provided the supplied pattern is not intrinsically valuable or constructed in a material that makes cutting difficult or impossible. Pattern cutting is usually the only option if an artwork has to be divided for sand moulding, so it is vitally important to construct large scale sand patterns in a way that makes easy sectioning possible. If a pattern is to be cut up, it is essential to consider the position and nature of any armature wire used. Chicken wire and other mesh for instance, is very difficult to cut through without causing severe damage to fine plaster finishes. If a pattern armature passes through a cut line, it is best to use either aluminium or else a light gauge steel bar for the support. It is also a good idea to avoid placing more than one armature bar in the proximity of a likely cut.
Alternatively, it is sometimes possible to construct the reproduction mould in a way that divides the pattern. An example of this is if the founder wants to section a life figure for casting, but has to keep the artist’s original pattern in one piece. Instead of cutting the pattern itself, the founder instead builds a series of abutting rubber moulds around the complete pattern, one for each leg and arm, the torso, the head and so on. Once all the moulds have been completed and removed from the pattern, they can be used individually to produce wax patterns for each section of the figure (see REPRODUCTION MOULDING).
Another approach is to mould the pattern without regard for cut lines. The founder then uses the rubber mould to produce a complete wax pattern. It is this wax version of the artist’s master pattern that is then cut into appropriate sections for casting. This procedure is quite common in foundries using the ceramic shell system. Waxes made for this investment system do not usually have a heavy core inserted, but are often cut in a way that allows the easy drainage of excess investment slurry, (see also WAXWORKING and INVESTMENT).
If you are going to section your master patterns for casting, here are some basic guidelines:
Avoid cutting through intricate details and forms if at all possible.
Avoid cuts that follow along natural breaks (such as elbow and knee creases or limb joints (groin, armpit etc). This can make relocation and reconstruction difficult. As a general rule, follow high points of form or contour.
Cut patterns into as few sections as possible and try to keep sections ‘in the round’, this helps to retain the basic shape of cut volumes and avoids reducing sections to curved panels, which can be difficult to reconstruct as coherent volumes.
Keep cut lines simple and fairly straight, a wavy or offset line can aid registration and help disguise a welded joint, but too much variation can complicate reconstruction.
If roman joints are not used, incise a series of registration marks transversely across the cut line to enable accurate location of the cast sections. It is also common to put a notch or ‘set’ into the cut line to assist location.
Ask your founder for guidance, and follow any direction given. If in doubt, let the foundry section the pattern.
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