Plaster Casting

Gipfelwert, m. top (or peak) value, maximum. GIpa, m. gypsum calcium sulfate plaster of Paris. >abdruck, abguss, m. plaster cast, -arbeiter, m. plasterer, gipsartig, a. gypseous. 

Gips-erde, /. earthy gypsum gypseous soil, -form, /. plaster (Paris) mold. gu(h)r, m. earthy gypsum, -guss, m. plaster casting, plaster cast. 

Question 10.4 Why Does a Plaster Cast Warm as the Cast Hardens ... 

Plaster casts are often used to hold an injured joint or bone in place to facilitate healing. As the plaster cast is applied, the patient often notes that the plaster cast feels warm. Chemistry provides an explanation for this observation. 

The plaster cast forms through a chemical reaction upon the addition of water to Plaster of Paris. This reaction releases heat, warming the hardened cast. 

When Plaster of Paris, CaSC>4 5H2O (s), is mixed with water, solid gypsum, CaS04- 2 H2O (s), is formed in an exothermic reaction, that is, a heat-releasing reaction. Thus, as the cast hardens, the plaster cast becomes warm ... 

J. M. Szymanski (1973, 1979) successfully applied Scott s method to surface strength tests with plaster casts. A near-surface layer of higher strength in relation to the interior of the cast was found to develop while the casts were drying (Fig. 4.4.5). The concept of laminar abrasion resistance WSic was introduced and defined as the reciprocal of the derivative of a function Am — that is,... 

Fig. 4.4.5. Scott s surface abrasiveness of plaster cast made at WjG = 0.8 according to amount of make-up water evaporating in the drying process on unit area.

Calcium sulfate For making plaster boards, plaster casts for injured limbs... 

Mrs Patel is a frail (BMI 18) lady of 72 with well-controlled asthma using high-dose steroid inhalers and occasional oral courses during an exacerbation. She came in to show you her wrist, which is in a plaster cast. She wants your opinion as the orthopaedic consultant has said she has got osteoporosis and wants to send her for a special X-ray and start treatment. 

Most molds are thin shell-like structures made from metals. Molds made from other materials (plaster casting, reinforced plastics, wood, etc.) are used for special applications. Lightweight cast aluminum and electroformed or vaporformed nickel molds, which are light in weight and low in cost, can be used. Aluminum molds are very popular especially for small to medium-size products. Aluminum has better heat... 

Indirect tooling methods are many. Examples include cast aluminum, investment metal cast, cast plastics, cast kirksite, sprayed steel, spin-castings, plaster casting, electroforming, room temperature vulcanizing (RTV) silicone elastomer (Chapter 2 Silicone Elastomer), elastomer/ rubber, reaction injection, stereolithography,338 344 (Table 17.4), direct metal laser sintering, and laminate construction. 

I sent it off to the forensic lab for spectroscopic ana is, something I had neither the expertise nor equpment to carry out iryselfi and started making plaster casts of the knife cuts in the bones. If the weapon that had caused them was ever found, it would be possible to identify it simpfy by seeing if it fitted — a match every bit as conclusive as Cinderella s slipper. 

Allergic dermatitis has been demonstrated from direct skin contact and from exposure to gaseous formaldehyde in the air. Various forms of reaction occur, from simple erythema to maculopapular lesions, hyperesthesia, and angioedema. Five patients developed an allergic contact dermatitis to plaster casts, caused by free formaldehyde released by a melamine-formaldehyde resin incorporated in the plaster. 

Penna F1ex. (Perma-Flex Mdd] Polysulfide or silicone systems for making elastic molds and patterns, for precision casting, plaster casting and foundry pattern material. 

Conventional molds, such as plaster-cast aluminum, are satisfactory for ECTFE molding. A comer radius greater than 1.25 cm has been recommended to produce a smooth interior surface and uniform wall thickness. To facilitate release from the mold, silicone or fluorocarbon release agents can be sprayed in scant amounts on the mold surface. Venting of the mold is recommended. 

For the production of plaster casts used to immobilize broken hones ... 

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