Silk

New Zealand Journal of Agriculture, Volume 100, Issue 3, 15 March 1960, Page 294

Silk

Jdts dharacteristlcs and it& (dare

By

MAUD B. STRAIN,

Home Science Instructor,

Department of Agriculture, Dunedin

PURE silk is a most desirable fabric because of its unique properties. It is soft and supple yet resilient, sheer but strong, warm though light in weight. Pure silk materials have been unprocurable for a long time and a generation has grown up unfamiliar with this beautiful fabric. It always has been, and may remain, a luxury fabric, but it is beginning to appear again in the shops and so it is advisable to know what to look for when buying it and how to care for it in use. Silks properly treated will give excellent wear and will retain their elegance for years.

'T’HE only source of the silk fibre is a cocoon spun by the silkworm, a species of caterpillar. There are several species of silk-producing cater-

pillars, but the mulberry silkworm produces most of the commercial fibre and they have been artificially cultivated for centuries. There are other varieties of caterpillars which cannot be artificially cultivated and they produce the fibre known as wild silk. When the caterpillar is fully grown it spins a cocoon round itself. If left

alone, it would emerge after two weeks as a moth, but as . this would mean that the cocoon would be ruptured and the great length of continuous filament reduced to lengths of a few inches, the cocoon is heated or steamed to kill the moth. After the moth inside has been dried the silk is unwound (“reeled”), the filament being 1,000 yd or more long. The filaments of several cocoons are then twisted together to form a thread (“thrown”).

Silk fibre as reeled from cocoons still has a gummy coating and in its manufacture into fabric it goes through ■ various processes during which the gum is removed, until with all the gum removed it becomes beautifully lustrous and luxuriantly soft. Silk foulard and the various wild silks still retain much of the gum on the fibre.

As well as the unbroken filament from undamaged cocoons, there are short filaments obtained from damaged cocoons and others which appear at various stages in the manufacture of silk. These short fibres are known as silk waste and are spun to produce threads in the same way as short fibres of cotton and wool are converted into threads. The thread spun in this way is known as spun silk.

Spun Silk

Spun silk is natural silk, but as it is

made from short fibres, it has slightly less strength and elasticity and is not as lustrous as reeled silk, though it has the same general characteristics. It washes well and is a good summer dress material. It is also used for blending with other fibres, particularly wool when it increases the wear and decreases the shrinkage. Other uses are for trimmings, sewing silk, pile fabrics such as velvet, and umbrella coverings.

Wild Silk

Wild species of silkworm live on oak leaves. They produce a coarser, less regular filament which is tan in colour because of the tannin in the oak leaves. Wild silk does not take dyes as readily as the cultivated variety but it can be dyed satisfactorily in plain colours.

Fabric made from wild silk is very strong and has a crispness and handle that make it suitable for tailored coats and suits beside frocks and blouses. It washes well and is easy to iron, but it must be bone dry before ironing. If ironed damp, it has a papery feel because of the presence of the natural gum on the fibre.

Shantung and tussore are both wild silks. Properties of Silk When silk fabric is well constructed it is very durable; its use for parachutes is the highest recommendation that could be given as to its strength. It is smooth and lustrous because of the length and regular shape of the fibre, and it is elastic, being able to stretch about one quarter of its length without breaking. Because of its resilience, silk is crease-resistant; a silk handkerchief crushed to a ball in the palm of the hand will jump right out of the hand when released. Silk, like wool, is a non-conductor of heat and is warm in winter and cool in summer. It is hygienic because its smooth surface does not attract dirt and any dirt that does gather is given up readily when the material is washed or dry-cleaned. All silks spot with water, but subsequent washing or drycleaning restores the appearance of the fabric. Strong acids attack silk, but dilute acids have no effect. The peculiar crackling sound heard when silk is rubbed together or squeezed in the hand comes from the fibre being washed in a dilute acid bath and being dried without rinsing. It disappears after washing. ' Strong alkalis such as caustic soda destroy silk. Strong soaps should not be used on silk because they may contain an alkali. Perspiration, being acid and salt, should be washed out immediately. Other than under extreme conditions of dampness as may occur in tropical countries, silk is not subject to mildew, but should not be left damp for long periods. Normally it dries out before mildew has time to develop. Silk takes dyes well and is especially suitable for printed designs. Dyed silk is colourfast under most conditions, but not to strong sunlight. Silk fabrics are made in a great variety of weights and textures from fine, sheer chiffons, georgettes, and similar gossamer fabrics through all the intermediate weights and textures to heavy brocades and satins. W-qV As much as 25 per cent of the weight of raw silk is lost in the degumming process. To offset this loss metallic substances are sometimes added in the dyeing process to make no the weight. Weighted silk fabrics have become acceptable in the textile industry, but if excessive metallic salts are used in the weighting, they eventually weaken the fabric.

Weighted silk is less compactly woven than unweighted silk and less silk is used in the construction of the cloth; in other words weighting rather than compact construction gives firmness and body to the fabric. A small amount of metallic weighting correctly applied to a fabric that is woven to hold it is not considered injurious. It lowers the cost, and gives the silk crispness, lustre, a firmer body and feel, and when the fabric is pleated it retains the crease. However, the natural elasticity of the silk fibre is lost and it is subject to deterioration when exposed to sunlight, perspiration, and dry-cleaning. Taffeta is a fabric often heavily weighted and it will crack and split at places subjected to strain in wear or when folded for a long • period. Rayon taffeta does not contain metallic weighting. identification A rough way of identifying silk is by the burning test. Pure silk burns slowly and ceases flaming when the fire is withdrawn. The ash appears in the form of round, crisp, shiny black beads that crush easily between finger and thumb. Acetate also leaves a black bead, but

it is hard and brittle, and very difficult to crush. Also, acetate blazes as it burns. Weighted silk burns without showing a visible flame. The burned part becomes incandescent, chars, and gradually smoulders away, leaving behind a skeleton of the original fabric. Trade Description It is necessary to understand the meaning of the various terms used to describe silk before one is able to judge the quality of a silk fabric. “Silk” means the natural product of the silkworm. “All silk” may be applied to fabrics containing no other textile fibre, but an all silk fabric can contain weighting. “Pure silk” is used only where there is no metallic or other weighting except that which may be an essential part of dyeing. “Pure dye silk” indicates that there is no metallic weighting and the fabric is made exclusively of silk fibres. However, there still may be water-soluble substances such as starch, glue, sugar, or gelatine which may help to give firmness, but as these are removed at the first washing or cleaning, they have no detrimental effect on the silk fibre. Well constructed pure dye silk requires a greater amount of silk

thread than weighted silk because pure dye silk is usually more compact,

Thus .it is generally superior, having the qualities of elasticity and durability because the natural elasticity of the silk fibre has not been lessened and its great natural strength has been retained. “Nett silk” is a high-grade pure silk.

Silk fabric names, such as shantung, crepe de Chine, organza, if used to describe fabrics not made of silk, should always be qualified by the name of the fibre from which they are made, as cotton . shantung, nylon organza, or rayon crepe de Chine.

Care of Silk

Silk is a strong fabric and will give long wear if treated carefully. Fabrics such as taffetas, brocades, and multicoloured prints should be dry-cleaned, not washed.

Silk should never be allowed to become very soiled before washing or dry-cleaning. Stains can often be removed by washing immediately in warm soapy water. If they have dried in, it is better to send the garment to be dry-cleaned rather than try to remove them chemically at home.

Perspiration quickly rots silk. Underarms of dresses and blouses should be protected against perspiration and if staining occurs, it should be washed as soon as possible. If it dries in the fabric, it is often impossible to remove.

Silk garments should not be put away for any length of time without being washed or dry-cleaned. Moths will eat dirt off silk and damage it in the process, but they will not attack the clean material.

All kinds of silk can be ironed to smooth out wrinkles, but the iron must be cool.

Laundering

Before washing silk articles test for colour fastness. Wet a small piece of fabric in tepid water. Take a piece of white material and place it over the fabric and press with a warm iron. If no colour comes off on to the white material the silk fabric is colour fast and thus washable.

If there are no scraps' of material to test, wet a piece of white material and place it on an inconspicuous place on the silk, such as on the seam allowance inside the skirt, and press with a warm iron. If any colour comes off on the white material the silk is not washable.

The construction of a garment and any trimmings on it must be considered before deciding to wash it.

Silk should not be washed in hot water and it must not be soaked or

boiled. As it does not hold dirt strongly, it should be washed by

kneading and squeezing in warm soapy water. Use good-quality soap flakes and avoid strong bar soaps. Soiled parts such as collars and cuffs should be laid on one hand and rubbed gently with the other, using extra soap flakes if necessary. It is more satisfactory to wash silk articles by hand, but if they must be washed in a machine, they should first be put in a bag made of some loosely woven material. Silk should be rinsed twice in cool water, then rolled in a towel and the excess water patted out. It should never be twisted and it

should not go through the wringer. It. can be put out to dry in an airy place away from the sun or any direct heat. Silk should be ironed on the wrong side with a warm iron when slightly damp; if dried and re-damped it will look patchy. Shantung, tussore, and other wild silks are ironed when bone dry. Crepe weaves always contract when wet, but may be eased back into shape during ironing. They should be ironed on the wrong side when slightly, but evenly damp.

Hazel Nut Cake

THIS is an unusual recipe for a delicious, very rich cake made from finely ground hazel nuts. No flour or butter is used, as the nut meat is rich in starch and oil. I first encountered this cake in Vienna and after may years of searching was given the recipe by a friend who grows hazel nuts in her garden near Nelson. In Vienna this cake is served as a torte lavishly decorated with sweetened whipped cream to be eaten with coffee which is also topped with whipped cream. This would be too rich for most people and a forbidden delight for waistline watchers. (A torte consists of three or four J to 1 in. layers of cake filled with thick, sweetened cornflour custard often flavoured with kirsch or some other liqueur. The top of the torte is decorated with piped whipped cream.) As a compromise serve the cake as a dessert with whipped cream and sliced fresh fruit or plain with coffee.

The illustration gives an indication of the size of the cake made from the following recipe. It was baked in a 9 in. sponge tin. Hazel Nut Cake 2 lb of hazel nuts 1 teaspoon of baking--4 eggs powder 6 oz of sugar Shell the nuts and mince the kernels very finely. Some oil will drip from the mincer and this should be saved unless it is very discoloured. Sift the baking powder, then beat the eggs until they are thick and creamy. Gradually beat in the sugar and fold in the ground hazel nuts, oil, and baking powder. Pour into a lightly oiled sponge tin and bake in a moderate oven (375 degrees F) forf- to 1 hour. —BETTY M. JOHNSTON, Home Science Instructor, Department of Agriculture t Wellington