acd producing fibrous casts

Level 3 Diploma in Plastering

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PowerPoint presentation

Casting detailed fibrous plasterwork

Unit 315: Producing and fixing detailed fibrous plaster and cement casts



Assessment criteria5.1 Different types of reverse moulds

5.2 Methods of casting

5.3 Different types of release agent



Reverse mouldsThis PowerPoint presentation will look at reverse moulds, methods of casting, and release agents used in producing and fixing fibrous plaster and cement casts.



Plaster reverse cornice mouldA plaster run reverse mould. This is run on the bench and cast to achieve a length of cornice.



Mould sealed with shellacOnce reverse moulds have been run, they are sealed with shellac and a release agent is applied.



Reverse moulds can also be made from fibreglass. They are light and easy to store.

Reverse moulds



Plaster piece mouldsPlaster piece moulds can also be used for casting in plaster or sand and cement. They can be made in several pieces.



The piece mould will fit together – where the pieces join, grease should be applied to avoid a seam showingin the cast.

Plaster piece moulds



Plaster piece mouldWhen casting from a plaster piece mould in sand and cement, oil is used as a release agent.



Plaster piece mouldCement is brushed onto themould to give a good even face, much the same asfirstings when casting inplaster. However, you should not splash the cement.



Plaster piece mouldThe semi-dry sand and cement mix is then gradually applied and compacted.



Plaster piece mouldSand and cement is then filled to the top and compacted up to the strike off.



Plaster piece mouldThe cast is then struck off flat.



Plaster piece mouldA bar or dowel is thenplaced in the castto allow for fixing.



Beam case mouldA beam case mould is a run loose piece mould that comprises of two cheeks and a soffit.



Beam case mouldThe two cheeks are runloose and butted up to thesoffit which is fixed to the bench.



Beam case mouldBeam case casts areproduced to cover an existing beam – such as an RSJ – or to create a false beam. Casts are struck off with a gauge to an accurate thickness.



Beam case mouldCasting is carried out as for cornice: two gauge method.



Beam case mouldTurning a spiral is produced with a turning box. Hinges allow the stock to be lifted clear and the profile cleaned.



Beam case mouldA drum is made on a tapered spindle. Plaster isapplied to the shellackedand greased spindle.The spindle is turned and as the plaster stiffens, the shape forms.



Small column produced from turning box/plasterers’ lathe.

Beam case mould



Beam case mouldOnce a spiral balastrade or small column model has been formed, the next stage is to produce a two-piece mould.



Beam case mouldA back and front mould orpiece mould is produced with joggles for accurate location of the pieces.



Beam case mouldA plaster case supportinga layer of pliable rubbermoulding material.

Note: the funnel hole where rubber is poured.



Beam case mouldDeeply contoured models may be covered with a controlled thickness ofrubber – either silicone or PVC.

This method avoids largepockets of moulding material.



Beam case mouldLips and joogles can beformed to lock the moulding material into the case.



Flood mouldFlood mould is made bypouring moulding materialover an open model ringedby a retaining wall.

Material is poured coveringthe highest point to form a flat back to the material.



Flood mouldA low-relief ceiling centre is an example of a mouldproduced in the flood mouldmethod.



Flood mouldFlood moulds can be used for panels and small sections of moulding.



Run case reverse mouldA run case reverse mouldproduced from a run core.

The core is formed over the model by covering the model in wet newspaper and running a profile. This is run off to core thickness.



Run case reverse mouldOnce the mould is poured, the case is taken off andshellacked. French chalk is applied to act as a release agent for the rubber.



Run case reverse mouldRubber is trimmed and the pour holes are cut to allow for the rubber tosit correctly in the case.



Any questions?

acd producing fibrous casts

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