All operations in the kitchen rely a great deal on the use of the eyes whether it be for finding the caterpillar in the cauliflower or deciding the delicate degree of browning required in potato straws. Even though other operations such as rolling pastry and mixing puddings do not require so high a degree of visual discrimination and judgment the eyes are constantly being used and efficient illumination is necessary at all points in the kitchen where work is in progress.
Reasons for Good Lighting
(a) It is essential that absolute cleanliness is maintained in all parts of the kitchen and in all the equipment used. No apology is made for emphasizing this point because the detailed work which alone can ensure cleanliness is too often neglected. Where kitchens are inadequately cleaned animal and insect pests are attracted by the particles of food left on the floors and tables, in the cracks and on the ledges. Thorough cleaning depends on a combination of several factors but one of the most important is the ability to see clearly what has to be cleaned. For instance, it is impossible to clean a large milk boiler without frequent and careful examination to see where further friction is required. For this as for all cleaning processes the standard of lighting must be good.
Furthermore, cleanliness in kitchen work extends beyond the cleaning of premises and equipment. Some foods, as for example vegetables, dried fruit, etc., must be cleaned before use, and a close watch must be kept on all foods to detect any undesirable extraneous matter and to remove it before the food is finally prepared. Unless these operations are performed in a good light, close supervision is not possible.
(b) It is well known that any piece of work is done more efficiently when conditions are comfortable and convenient. Less strain, both physical and mental, is placed on the worker, she is able to proceed with the work more quickly, and moreover, the onset of fatigue is considerably delayed. There must be a good light on any work that requires careful watching; a dim light or a light so placed that the shadow of the worker falls on the working area is a constant source of irritation. Admittedly the worker may be almost unconscious of the effect because over a long period she has become inured to conditions that are far from perfect. But one only has to improve the conditions to make her realize what she has been contending with and how much more easily and efficiently the same operation can be performed.
(c) An attractive appearance in the finished article is one of the aims of all good cooks whether it be in the delicate colorings and careful pipings on the iced cake for a special occasion or in the dish of plain boiled potatoes. If the lighting in the kitchen is poor it is probable that the cook will be dissatisfied with both of these products when they reach the bright light of the dining room. The carefully blended colors on the cake may appear crude when correctly illuminated and the potatoes may show signs of blackening which the cook would have prevented at any cost.
In view of the importance of good natural lighting let us examine briefly some of the factors involved. They are of two main types, those which can be measured, such as quantity of light and brightness, and those of a qualitative nature such as contrast, glare and colour, which cannot be readily measured.
The importance of these qualitative factors in relation to kitchen work is frequently not sufficiently appreciated. Good contrast plays an important part in vision because our eyes naturally tend to focus on it. A contrast that is too strong is, however, tiring, and if it is developed by light coming from one direction only, the shadow’s may be too strong. It has been found that the best results are obtained if the chief source of light on the object to be illuminated is mainly from one direction with supplementary illumination from another direction or from general diffused light. In the kitchen this means that operations requiring acuity of vision should be performed near to a window which will supply the main source of light and that this should be supplemented by either clerestory or lantern lighting, or by less intense light coming from windows at some distance away.
Another point to bear in mind when considering the principles underlying good vision is that the object under observation must be the brightest in the field of vision. If anything else is brighter, attention tends to be distracted. In its more intense form this distraction is known as glare and should of course be avoided. Bright metal surfaces, glass or moving water reflecting the light can produce this effect in the kitchen. A white table top can have the same effect if it is in the field of a strong source of light. Thus one should be careful in adopting pure white surfaces in situations where glare may occur. Color is another factor which has a bearing on the illumination of a room. The amount of light in a room is increased by light colored decorations and it is usual to find kitchens decorated in white or light colors both because of the extra illumination and because of the impression of cleanliness which these colors give.
The quantity of daylight entering a room is the most important single factor affecting the illumination, and this varies according to different conditions, some of which are under human control and some of which are not. The sky is the source of light and since the intensity varies from winter to summer, from sunrise to mid-day and from cloudy to clear sky, the quantity of light avail able at different times and seasons will vary and cannot be controlled. However, certain conditions which affect the quantity of light can be controlled by giving careful thought to the size and placing of windows. The quantity of light reaching a given point in a room varies directly with the amount of sky that can be seen from that point. The unit used for measuring the efficiency of daylight admission to a room is known as the daylight factor. The maximum amount of illumination obtained from the sky is that which would be available at a point in an open field remote from all buildings or other objects. This is assessed as having a daylight factor of 100. If a point indoors receives five per cent of the total light available outdoors under an unobstructed sky this point is said to have a daylight factor of five. This fraction is really a measure of the amount of sky to which the point in question is directly exposed. Thus a point near a window will have a larger daylight factor than a point further away. Owing to the presence of nearby buildings and the smallness of the window the value obtained for this figure is usually of the order of a few per cent. The actual level provided in a kitchen should be a minimum of 4% and this can usually be achieved with the aid of top lighting.
It is interesting to see how the shape, size and placing of windows influence the intensity of illumination and the penetration of daylight. A tall high window gives much greater penetration than a long low one, while clerestory lighting is better still in this respect. Upper floor windows admit more light than those on the ground floor or basement, which are often obstructed by other buildings, nearby walls at right angles to the plane of the window or overhead balconies. Another factor which influences distribution of light in a room is the height of the sill in relation to any adjoining working surfaces such as tables or sinks. A high sill will cast a deep shadow across the sink or the table, being particularly noticeable in a deep sink. It is therefore advisable that the sill should be not more than six inches above the top of the sink.
Operations Requiring Good Lighting
As has already been stated almost all kitchen operations require a good light for their execution and a good general light is necessary over the whole of the kitchen area. In such operations as washing up and vegetable preparation, its importance is obvious and it is equally necessary for all working tables, but there are some operations where the need for good lighting is not always appreciated. Thought should be given to the placing of equipment to obtain good lighting at points where it is required. For example, ovens in a central block of equipment should be so placed that the doors open towards the light. Or, if the light comes from the side, care should be taken to choose ovens with doors hung on the better side. Good lighting is required on boiling tables and on fish fryers and careful planning can usually ensure this.
Artificial Lighting
When we come to consider standards of artificial illumination it is possible to be more precise in making recommendations. The illumination of a surface is measured in units known as foot candles. One foot candle is the intensity of illumination on a surface due to the light received at that surface from a standard candle twelve inches away. An alternative unit for the measurement of illumination is the lumen, which is the amount of light falling on a surface of one square foot, every part of which is at a distance of ift, from a standard candle. Put in another way we can say that where the intensity of light on a given surface is 1ft. candle, this surface is receiving 1 lumen per square foot.
Now that there has been a national decision to adopt the metric system this has necessitated a change to the Système International d’Unités (S.I.) which is a nationalized system of metric units now coming into international use. The S.I. unit of illumination is the lux (one lumen per sq. meter) and imperial units (lumen per sq. ft.) can be changed to S.I. units by multiplying by a factor of 10.76.
The requirements for different operations can be stated quite accurately. For close careful work such as sewing an exceptionally high standard of illumination is required and 600 lux (55 lumens per sq. ft.) are usually recommended whereas for general lighting on staircases an illumination of even less than 200 lux (18 lumens per sq. ft.) is acceptable. The standard of illumination in kitchens lies between these two, a value of 300-400 lux (27-37 lumens per sq. ft.) being suitable, the former for dining rooms and the latter for kitchens. This intensity can be achieved either by general illumination throughout, or by individual fittings arranged to provide the desired standard at working points, or by a combination of these two methods. If general lighting throughout is chosen, it must be realized that the level of illumination is affected by factors other than the power of the light source and the height of the fitting: the size and height of the room, the amount of light reflected by the surroundings and the distribution of light from the fitting also play important parts. Thus although it can be stated that 200 watt fittings fixed 9′ 6″ above floor level at 10′ centers give the required standard of illumination of 6-10 foot candles, clearly this is only a general recommendation and the factors already mentioned will have a bearing.
lo kitchens where hoods are provided for ventilation, lighting arrangements require careful planning to ensure that there is satisfactory illumination on the surfaces under the hoods. In many cases this can be effected only by providing individual lights attached to the hoods themselves.
Another point to which insufficient attention is frequently paid is the design and accessibility for cleaning of the fittings. It is inevitable that fittings in kitchens become coated with dirt and grease and for reasons of hygiene as well as of efficiency they must be cleaned frequently. This is clearly not possible if such an operation requires the attentions of a man on the top of a twenty foot step ladder.
It is not proposed to enter here into a long discussion on the relative merits of filament and fluorescent lighting for kitchens. The latter method is popular because of the low running costs entailed and because the shadows cast are less pronounced than those from filament fittings. It is, however, very important if fluorescent lighting is chosen, to ensure that it provides for a satisfactory color reproduction as it is disturbing to have colors unduly distorted by artificial light.