It has taken exactly three weeks for a batch of natural refined beeswax (pellets, basically yellow) to fade by sun-bleaching behind my window. I laid it behind the window of my tiny apartment in Madrid exactly the 14th February (how to forget the date) and yesterday it was as white (sort of creamy… OK, Pantone 7500) as the chemically bleached one.
It is not the first time I do it this way, but it is the first time I record it as an experiment in order to draw conclusions that I hope will be interesting for you, specially if you live in Europe where is absolutely impossible to get other white beeswax than the chemically treated (of course unless you get it from USA which is not very economical or even reasonable).
For less than a few years I had never heard about the Dilco refinement process, or the diatomaceous filtration, but living in country with a strong catholic tradition like Spain, you learn that there are not better candles than the 100% natural yellow beeswax ones; actually, not long ago, they where the only allowed by the Vatican as a symbol of purity. Natural beeswax candles melt, smell and speckle differently, and the Seville Holy Week Nazarenos (not to be confused with a Ku Klux Klan member), know what I am talking about…
There is an easy and economical way of encaustic wax sun bleaching at home or in the studio: solar bleaching, less harmful to the structure of the materials than chemical bleaching (chlorine / peroxide). Not long ago bleaching grounds were common everywhere in Europe, specially in the areas where the textile industry was based.
How much solar energy it is necessary for encaustic wax sun bleaching
Well, it seems 3 weeks of exposure from February to first week of March is enough. Lets see what this means in terms of energy (see image below)
Solar insolation is a measure of solar radiation energy received on a given surface area in a given time. It is commonly expressed as average irradiance in watts per square meter (W/m2) or kilowatt-hours per square meter per day (kW•h/(m2•day)) (or hours/day).
The white area in the radiation chart represents the energy received in my window ( from 9:00h to 12.00h) from 14 February to 7th March. This means approximately 21 days * 3 hours/daily= 63 hours of sun exposure with average intensity of 3700 Wh/m2, that means a total energy received of 149.310 W/m2 (approx 150.000 W/m2)
The chart above is for a latitude of 40º North (NY or Madrid) but you can get the one of your area on internet.
So if I want to fade beeswax in May for instance in the same window the average radiation in May (orange) is 5.700 Wh/m2, so
150.000 W/m2 / 5700 Wh/m2 * 3 h = 8 days ( in May)
150.000 Wh/m2 / 6500 Wh/m2 * 3h = 7 days (in July)
This calculation is approximate, since UV radiation is not the only cause of fading and the calculation would need some daylight correction too. But my purpose is to show that in the case of beeswax solar fading is quicker than one might think, even in winter or in Norway (hello Debbie).
We are almost there… it can be that after the sun exposure, when your wax is in the cupboard waiting to be used, it becomes yellower. How can that be? I said the process is irreversible… don’t panic, is just the consequence of natural process called diffusion in which molecules naturally move from high concentration to low concentration in search of uniform distribution or “equilibrium. It is like smoke spreading in a room.
It takes from 1 week (best case) to 4-5 weeks (worst case) for beeswax pellets to fade the color, depending on latitude, solar month and daily direct radiation exposure.
The fading should have two phases to allow the diffusion process to take place, how long? difficult to say. I will store my ready faded beeswax pellets in a box today and will let you know what happens…
This post is also available in: Spanish