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the importance of eye safety in solar cooking

by  howard boldt   january, 2001

recently i became more aware of dangers to eyes in solar cooking.  i read some reports of eye damage, even blindness, so my concern grew.  i initiated more discussion about it on our solar cooking email discussion list (you may join or read archived comments through this site) and some of this information comes from there.

the greatest danger naturally exists in the use of focusing cookers.  of these, the parabolic type is the most common.  i intended to get some medical opinions on this subject before writing.  it would still be a good idea, but common sense tells us that exposing the eyes to light which is of an intensity greater than normal sunlight - perhaps many times greater - may result in serious and permanent eye damage.  i think the danger may also be heightened for those who are already weakened from living under physically stressful circumstances, such as inadequate nutrition.  their eyes may be less resistant. 

the box cooker holds some potential for flashes of intensified sunlight hitting the eyes.  for this reason, sci teaches users to approach a box cooker so that their shadow blocks the sunlight.  this is a good common sense solution. sunglasses could also be worn and other methods of attending to the box cooker could be devised, such as turning the entire cooker away from the sun in such a way that there are no adverse reflections.  box cookers with multiple reflectors and those with rear doors through which one can look towards the incoming sun pose slightly different problems.  but overall, box-type cookers are fairly safe and i am told that it is for this reason that sci promotes mainly these.

so, if box cookers are feasible, why not promote these?  but, since parabolics are also doing good in the world and because they are popular, we should also find the safest ways to use them.  in some cases parabolics seem to be cheaper and more effective than box cookers.  better box cookers can be built, but the material may not always be available for this.  and the parabolics already existing will of course continue to be used.

firstly, to use a parabolic safely, cooks should be thoroughly educated.  also, other adults and children who will be around it.  if people know that a grave danger exists in sticking their head into the zone of intensified rays, they will not do it intentionally.

secondly, the design of a parabolic cooker is important.  those which have a higher focal point have more danger because it is easier to accidentally put one's eyes in the wrong place.  eg solar is an example of a company which makes a parabolic dish with a very low focal point.  (see photo under "manufacturers" at this site)  the pot (the focal point) is about level with the rim of the dish.

thirdly, other safety features and advice can be sent with new parabolic cookers, and new features can be made and added onto old ones. fencing the cooking area has been used successfully.  naturally, this keeps people away from the cooker and gives a message that respect is required for the
cooker.  a well-built fence may keep children back.  also animals, who i suppose could suffer eye damage, too.  additionally, a fence protects a cooker from damage by animals and children.  so, i see this as one of the best ideas.  i think some cultures may be adverse to fences and supplies may be short, but if the need is understood, perhaps many families and villages would attempt it. putting the cooker out of reach might also be accomplished by other means such as moving it to a roof-top (where adequate roof-tops exist), but this may make it more susceptible to wind.  one person constructed a high platform to do all his solar cooking on and reports that he likes it very much.

similar to fencing off the cooking area, i have had the idea to create a wall or curtain which extends upwards from the rim of the parabolic dish.  this would make it very difficult to stick ones head into the danger zone. the effect is that of a "sunken' parabolic.  if the wall were made twice the height of the focal point, then the exiting rays coming back out of the top of the fence would be also returned to their normal intensity - should anyone look into this sunken parabolic form the top.  a further precaution would be to have a mesh across the top of the fence, preventing anyone from sticking their face down toward the focal area.  the wall might be made of sticks and fabric, or of woven materials.  a hole in the side of the wall would be necessary to reach the pot. additional structural bracing to the whole cooker unit may be needed to counter new problems with the wind.

whether this wall system is used or not, and whether a parabolic cooker has a low or high focal point, another way to help matters is to have a method of placing and retrieving the pot other than with one's hands.  this would prevent the cook from leaning towards the intensified rays.  one way to do this is to have the pot sliding across a rod or wire.  another way would be to build a "swing-arm", designed to hold the pot and move it forth and back, to and from the focal point.

sunglasses are sometimes worn when using parabolic cookers.  naturally they will afford some protection and i think those which also protect from side light would be even better.  however, i am wondering if glasses may in some cases give a false sense of security.  probably many types of sunglasses do not adequately protect, while the user's confidence in approaching the danger zone is increased.  this matter should be studied.  in any case, while potentially useful, sunglasses are probably in short supply in most impoverished areas of the globe.

these are the ideas which i can think of at this time.  i'm sure the debate will continue, as will our improved designs and innovations, and so we will no doubt arrive at more ways to make safer the wonderful science of solar cooking.  i look forward to more comments and articles helpful to this pursuit, especially from those who are more expert on the subject.  please send to this website and to the review.  also, you may join the discussion list and post comments there. and you may contact me directly.  my thoughts and experiments will be ongoing in the matter, as time permits.


fax:   306-239-4742

surface mail:       howard boldt
                          box 152 rr4
                          saskatoon, sk.
                          s7k 3j7

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