What Color is the Sky?


How do you transmit information about a color from generation to generation? It does not work to tell a person that something looks like  burnt sienna or cadmium yellow. In Jewish law, the same issue exists with volume and distance. We find examples of measurements such as the size of an olive, the size of an egg etc. This works as long as olive and egg sizes stay the same throughout history.

LycheeWhen it comes to color, it is very difficult to measure an exact color and pass on the nuances of the color. If someone says what color is a lychee or an apple, you have something in mind and it is generally a range of a color. When you are shopping for a fruit and it is outside of that range, you would likely reject it.

Shades_of_BlueWhen it comes to techelet, the idea that it should resemble the sea and the sky is also a range that you are looking at. Is it a clear blue sea. Is the sky a deep blue with fluffy white clouds or is it the pale blue I see out of my window today? To give us a clue, we can compare it to k’la ilan. Why? Because we know that techelet is supposed to resemble indigo-dyed wool so closely that the gemara had to come up with a test to discern the differences. It means that if we know the color of indigo-dyed wool, we might have an insight into the color of techelet.

While I have read that some reject the Radziner techelet because it does not resemble the color of the sky, the argument is problematic, because:

  • Nobody can say what the color of the sky is.
  • Ptil tekhelet tzitzit more resembles the sky over Pittsburgh than Jerusalem.
  • If techelet color is an identical match to k’la ilan (indigo) then Radziner techelet can be an exact match.


On the right is a photograph taken of some wool that was dyed with natural indigo (k’la ilan) by an expert in dyeing. As you can see, the colors vary from a pale blue to a deep blue. I am not a textile worker, but I would guess that someone dying fabric 2000 years ago, was probably not able to make an EXACT match of fabric from batch to batch.

As I write this, I am looking out of my window, which faces west, the direction of the Mediterranean Sea. The day started with a light blue sky and changed a number of times as clouds moved in and moved out. As the day progressed, the sky got darker, imitating all the shades of blue in this photograph.

techelet_stringsThe color achieved by the dyer depends on a number of factors, including the strength of the solution in the dye vat. As the active ingredients in the solution in the indigo vat becomes more depleted, the wool is dyed a lighter shade of blue. Other textile workers use a different technique to control the type of blue they want to achieve, they use the same bath, but dip the wool in a second or third time to make different blues. I am sure that if I put some Radziner techelet (see close up of Radziner techelet on the left) beside indigo-dyed wool, you would agree that the two can be considered identical.

I don’t know enough about the manufacturing process, but I suspect that the P’til tekhelet color also might change.  Baruch Sterman in The Science of Tekhelet, wrote: “Vitruvius mentions that there is a connection between the varied colors (purple through blue) obtainable from the snails and differing degrees of sunlight to which they are exposed. “For it does not yield the same color everywhere, but is modified naturally by the course of the sun… As we proceed between the north and west it becomes a leaden blue.”

I wonder if the shade of the wool, which forms the base  also makes a difference on what the final blue looks like.

More questions…



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