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A very science-y post. Fun! ©Science-y Hair Blog 2013 Dewpoint and relative humidity and how they effect hair has been swirling around my mind this spring as we have had some really variable weather. I live where winters are usually cold and dry, summer is usually hot and humid and spring and fall are combinations of everything. Dewpoint and relative humidity are not easy to understand. They're in the realm of physics - things like “saturation air pressure” that we experience every day and know what they are from experience. But when we try to measure them and predict and explain their effects on other complex systems like hair – Man! It’s not easy. Here’s what is wonky: Dewpoints getting into the “moderate” range, but dry air. You think your hair should be bouncy and defined, but instead it wants to be limp. But the dewpoint is above 40°F, you think – so what gives? When you go outside, your lips and eyes and mouth dry out and your waves and curls lose their spring or feel rough. ...

©Science-y Hair Blog 2013 I’ve wanted to post this for a while, but it makes me feel a bit subversive because I’m going to tell you that what you think you’re doing with hair conditioner is a wee bit wrong. This is my "ingredient-based" perspective. Not so many years ago, women washed their hair with bar soap. Many of them knew if they used water from their rain barrels (rainwater) that their hair would shine – because rainwater is soft water so there is less soap scum left on hair. People did not wash their hair often. Nor their bodies. Especially in winter. Now that so many of us shower daily and have hundreds of soaps and shampoos to choose from, it’s easier to over-cleanse the hair. Enter the “cream rinse.” A cream rinse is the ancestor of modern conditioners. – in the U.S. it was Breck and Wella Balsam that led the pack with fairly simple formulas that helped detangle hair which was dried out from frequent shampooing or damaged by teasing or hairspray and a multitude of ...

The last post was all about the dewpoint. On a normal day, that's the measurement that tells you how much water you might expect to be in the air - so you know whether your skin and hair will be dehydrating or not. ©Science-y Hair Blog 2013 Relative humidity is how much moisture the air is actually holding right now, vs. (relative to) how much it can possibly hold (the dewpoint). I am looking at a temperature of 67°F (19°C) with a dewpoint of 60°F and a relative humidity of around 80%. This is very juicy air! We are expecting strong storms from an air mass like this. It is usually foggy and very dewy in the morning when the air temperature is this close to the dewpoint and it's not very cold . When the dewpoint is close to the temperature, the air is wet. I think this is some of the worst "weather" for maintaining bouncy waves and curls because the moisture is being taken on by the hair and the wave and curl is expanding in some places, tightening in others and just n...

Doubtless you have read about dewpoint and what it means for wavy and curly hair. Generally, wavy and curly hair looks better when there is a “just right” amount of water vapor in the air. The important thing to remember is that we Always Obey the Laws of Thermodynamics! Things tend to come to a state of equilibrium. If there is more heat in your house than outside and you open a window, the warm air rushes out. If you place a glass of iced tea on a table on a hot day, the ice melts and the tea warms as it absorbs heat from its surroundings. ©Science-y Hair Blog 2013 Too little water vapor in the air and hair tends to lose moisture to the drier air. Too much water vapor in the air and your hair takes on a lot of moisture and begins to curl more – getting bigger and less defined (frizzing). Just right – and your waves and curls look healthy and defined. But I need pictures. I love concepts, but for mental recall – flashing back to a picture is so much simpler. First of all, dewpoint. Wh...

This post is timely to those of us in the Northern Hemisphere - to our friends and family in the Southern Hemisphere - hope you are enjoying spring into summer! Humidity is water vapor suspended in the air. How humidity is measured: Dewpoint – the temperature at which the air is saturated with as much water as it can hold, and so dew (or fog) forms. Dewpoint tells us the most about how dry the air is. Unless a new air mass moves in, the dewpoint can stay the same all day. This is what you want to watch to know just how moist or dry the air is. Dewpoints below 50° F (10° C) are “dry.” In the 50s  (10-15° C) is “comfortable” 60-65° (15- 18° C) is “muggy” 65-70° (18-21° C) is “humid” 70° (21° C) and greater is “oppressive” – rainforest-y - you feel you need to grow gills This is important for hair because dewpoint tells you how much moisture is in the air. Except for hair which has a very strong curl pattern, low moisture in the air tends to lead to flatter, less defined wavy or curl...