Stan Walerczyk



On December 16, 2013 Katie wrote and snail or whale mailed the following letter

to Stan Walerczyk, who has briefly met her and knows her father, who has a

general understanding of lighting. Katie and her parents allowed her letter with

last name and address removed to be posted in the Human Centric Lighting

website. There are not that many young people getting into lighting, and maybe,chateau gonflable

just maybe, Katie will be one who does.


Dear Mr. Walerczyk,

I hope you are doing well!

I am in sixth grade now and doing a report about blue light and how

it affects sleep. I have done a little research and know the basic facts on

this topic. I understand that you know lots about this topic. I would love to

know more the characteristics of blue light and it affects your brain,

leading to sleep issues.

If you can, please send me one or two reports or websites that you

think will be helpful in my report.

Thank you so much for your help!

Happy Holidays!



Stan received the letter on December 30 and emailed Katie the next day.

Following is a slightly modified version.

Dear Katie


It really made my day yesterday, getting your letter.


As you may have already found out, white light with significant blue

content, specifically around 480 nanometer wavelength, suppresses

production of the hormone, melatonin.


This is good in the morning and daytime, but not one to three hours before

going to bed, because melatonin helps people go to sleep.


So one to three hours before going to bed, people should have relatively

low light levels and a warm color tone of light.


Bluish light from computers, tablets and cell phones should also be

avoided before going to bed. Here is a free download that I use to reduce

that bluish light.

I thought you and maybe also your parents may like this TED Talks video.


Here is an LED bulb that is designed to be used before going to bed. You

can also watch the training video.


Since you are a student, high light levels and high Kelvin can be good

during the daylight. Here is a video.


Maybe I could work with your parents to improve the lighting at your



Here is another website. I am chair of the Human Centric lighting


HCL Home


If you do not understand something, you could ask your father first, and if

that does not work, you can email or call me.


I can provide more information if you want it.


Happy New Year and hope you do well on your project.




Stan Walerczyk, HCLP, LC, CLEP

Principal of Lighting Wizards

Chair of Human Centric Lighting Committee

P.O. Box 532634

Kihei, HI 96753


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