Running moulding on a bench

Running Moulding on a Bench Understand preparation of the bench and the running of positive and negative mouldings

Introduction to running on the bench Aims: Introduction to running on the bench Objectives: To know the difference in preparing a bench for a positive and negative mould. 3

Introduction: what do you know: 1. What are benches made from. 2 Introduction: what do you know: 1. What are benches made from? 2. how do you prepare bench for a positive mould ? 3. how do you prepare bench for a negative mould ? 4. How do we prepare a negative mould for casting? Work in groups or as individuals Set a time limit for the questions 4

Benches: Benches are usually about 3m long and 1m wide for running but if also used for a lot of casting can be 2m wide. Traditional benches where built on a timber frame with a bed of lightweight plaster and EML in for strength and finished with casting plaster around 25mm thick this was sealed with shellac and repaired after each use. Bench tops can be made of plywood (Marine ply being the best) which is also sealed with shellac. Some use laminate tops these are very good for casting off. When fixing a rule to bench ensure it is straight if is not your moulding will not be straight. Points for discussion: Internal and external uses. Different materials EML is made from and where each would be used 5

Running a positive mould Prepare the bench fill in any nail holes etc. Grease bench running rule and running mould Mark running rule the length of moulding you require Fix a headless nail at highest point of the template beyond the length required to stop mould slipping. You can place a clay piece in the shape of a cone over the nail to ease removal. Mix plaster into bowl of clean water let it soak then mix with hand to ensure there are no lumps Start to pour plaster and run mould pulling it against the running rule and the other hand holding down the nib. Keep using plaster ( whilst workable) and keep the running mould clean. You may need to mix another mix to finish and leave arrises sharp. Clean bench and running mould, remove mould by using a clean greased gauging trowel by sliding it under the finished from one to the other slowly lift and store on a flat surface to stop twisting. Points for discussion: Fixing Process for metal firing, wood and masonry 6

Positive mould for running curved work Running is the same just the position of the hands and mould should be taken off and put back in the same place

Running a Negative moulding (Reverse mould) a) Usually the size of the moulding means fixing a muffle to the running mould this can be made from Plaster or thin plywood or metal. In all cases it should fit 6mm in front of the template. b) You can save material by helping fill the core using plasterboard polystyrene or old moulding. c) Because you do not want this mould to move Clot nails with heads o are fixed every 450mm d) Grease bench and running mould and mix lime sand with casting plaster and run down the core. When set key using a craft knife. e) Remove muffle clean running mould grease bench and running mould and finish as described in running positive . f) Clean bench cut ends of reverse mould square to length required and prepare by applying 3 thin coats of shellac when moulding has dried out ready for casting off.

Reverse Mould

You now should have the knowledge to complete the following: 1 You now should have the knowledge to complete the following: 1.What are benches made from? 2. how do you prepare bench for a positive mould ? 3. how do you prepare bench for a negative mould ? 4. How do we prepare a negative mould for casting? 10