Workshop Technology
Sand wash is a casting defect which

Occurs as sand patches on the upper surface of a casting
Results in a mismatching of the top and bottom parts of a casting
Occurs near the ingates as rough lumps on the surface of a casting
Results in general enlargement of the casting

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Workshop Technology
The purpose of a riser is to

Act as a reservoir for the molten metal
Deliver the molten metal from pouring basin to gate
Deliver molten metal into the mould cavity
Feed the molten metal to the casting in order to compensate for the shrinkage

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Workshop Technology
Riddle is used for

Moistening the sand around the edge before removing pattern
Smoothing and cleaning out depressions in the mould
Cleaning the moulding sand
Reinforcement of sand in the top part of moulding box

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