CHAPTER III

PLASTER

Plaster, is a type of building material based on calcium sulfate hemihydrate,

nominally CaSO4·0.5H2O. It is created by heating gypsum to about 150 °C.

When the dry plaster powder is mixed with water, it re-forms into gypsum.

Plaster is used as a building material similar to mortar or cement.

Like those materials plaster starts as a dry powder

that is mixed with water to form a paste which liberates heat and then hardens.

Unlike mortar and cement, plaster remains quite soft after drying,

and can be easily manipulated with metal tools or even sandpaper.

These characteristics make plaster suitable for a finishing,

rather than a load-bearing material.

Some variations of plaster that contain

powdered silica or asbestos may present health hazards if inhaled.

Asbestos is a known carcinogen when inhaled in powder form,

especially in people who smoke, and inhalation can also cause asbestosis.

Inhaled silica can cause silicosis and encourage  the development of cancer.

ISOLATION DEVICE

The necessity of  isolation devices is connected to the development of electricity applications, in particular to the telegraph.

The  line made by Samuel Morse around 1840, used to connect Baltimora to Washington, was the first place where isolation devices were used.

Today these objects are precious and rare. Although in previous times  there were a lot of different industries that created these particular technical instruments  made of porcelain or glass.

Following is a list of the Italian companies  and the year of the last production:

Richard Ginori-1981

Verbano-1965

Ligure Vaccai-1977

Fil-1924

Imec-1980

Fip-1970

Bottacchi-1969

Eb-1950

Miva-1980

Vmr-1943

WAX

Paraffin wax is made of long-chain alkane hydrocarbons.

-plastic (malleable) at normal ambient temperatures;

-a melting point above approximately 45 °C

(113 °F) ;

-waxes from fats and oils;

-a relatively low viscosity when melted (unlike many plastics);

-insoluble in water;

-hydrophobic;

Waxes may be natural or artificial.

In addition to beeswax, carnauba (a plant epicuticular wax) and paraffin (a petroleum wax) are commonly encountered waxes which occur naturally. Chemically, a wax may be an ester of ethylene glycol (ethan-1,2-diol) and two fatty acids, as opposed to a fat which is an ester of glycerin (propan-1,2,3-triol) and three fatty acids.

It may also be a combination of other fatty alcohols with fatty acids.

PETROLEUM JELLY

vaseline is a semi-solid mixture of hydrocarbons, originally promoted as a topical ointment for its healing properties.

Petrolatum is a flammable, semi-solid

mixture of hydrocarbons, having a melting-point usually ranging from a little below to a few degrees above 37 °C.

It is colorless, and devoid of taste and smell when pure.

It does not oxidize on exposure to the air,

and is not readily acted on by chemical reagents.

It is insoluble in water.

It is soluble in chloroform, benzene, carbon disulfide and oil of turpentine.

EPOXY

epoxy or polyepoxide is a thermosetting epoxide polymer that cures when mixed with a catalyzing agent or "hardener".

The applications for epoxy-based materials are extensive and include coatings, adhesives and composite materials such as those using carbon fiber and fiberglass reinforcements for their excellent adhesion, chemical and heat resistance, good-to-excellent mechanical properties

The primary risk associated

with epoxy use are:

-oestrogenic activity;

-alteration of male reproductive organs;

-early puberty induction;

- breast feeding;

-pancreatic cancer