Capillary Action

Caught up in Christmas spirit and partying too much yesterday makes me realize I have a young spirit in a very old body. Today it has let me know I’d overdone it an that’s the reason for being late in posting this week.  With the season well upon us I’ve chosen to write about some of the science in picking out a Christmas tree and caring for it. 

Of the three kinds of evergreen trees usually used - spruce, fir or pine - I prefer the fir because its needles stay on longer and I find it is the easiest to decorate. If you click on video you’ll get a few tips on how to choose your tree and care for it. Best to wait until you get the tree home before using a saw to cut off about an inch thick slice from the tree trunk and then put it in a stand that holds water. We don’t think about it much but a tree is just like a cut flower, to stay fresh it needs to have its freshly cut end in water.

Any growing plant needs a constant supply of water to run up the length of its stems to carry nutrients so it can grow and mature. The water evaporates from the leaves [or needles] and though we are not aware of it, a big leafy tree can give off well over 100 gallons [~ 400 liters] of water a day. The water climbs up a plant or tree by capillary action, which is just the ability of a liquid like water to flow up narrow spaces in spite of the force of gravity pulling on it.  We are used to this effect when we see porous materials like sponges or paper soak up water, or paint being held between the hairs of a paintbrush.  As seen in the diagram, the narrower the tube, the higher the water can climb.  When you consider that the tallest tree  is almost 400 feet [120 meters] in height - that's figured to be the maximum height possible - you wonder at the power of  capillary action!

Being a chemist by nature, I like to think of the inter-molecular forces that are responsible for lifting water to such an incredible height. In my post on water  I discussed the uneven distribution of electrostatic charges around the water molecule that tends to make them stick together. In the case of plants or trees, the water molecules are attracted to the sides of pores and also to each other with the result that the combination of these attractive forces has the power to lift the water to the highest branches of the tree where the water evaporates causing more water to rise. The fun drawing below shows anthropomorphized water molecules climbing and pulling neighbors with them. 

You will be surprised I think at the amount of water your room temperature Christmas tree will need to stay fresh. As the water rises and evaporates from the needles it has the added advantage of supplying moisture to the dry air in your house. Sometimes you are advised to add a nutrient like sugar or aspirin to the water but the tree is not growing, so it really doesn’t need any.    Rie

Useful Gifts

The posting of my Sunday morning blog has become somewhat of a compulsion for me and until last Sunday I haven’t missed since I can remember. However illness in the family has taken precedence this week. Still I hope today’s subject is timely for those who, in this traditional gift giving time of year, are trying to think of interesting/useful and reasonably priced gifts for those who have everything.

Pictured on the left is a wine cooler.  It is an unglazed pottery cylinder sized to hold a wine bottle. The trick is to take your cooled bottle of white wine out of the frig, put it in the cooler that has about ¼ cup of water in the bottom and put it on the dinner table.  The water seeps into the clay and evaporates taking the heat energy from its surroundings to do so and keeping the wine cooled indefinitely. Try wetting your finger – its cooling illustrates the point. 

For centuries before refrigeration when people used to churn their own butter and needed to keep it cool, they used a similar technique. To make the process more convenient, in the 1600’s someone invented a butter bell as a way to store butter. As the video shows, butter is packed into the ‘bell’ and water is added to the base. The bell is then inverted and set into the base where it displaces some of the water so that it rises and seals the butter off from the oxygen and bacteria in the air. Originally, of course, the base was unglazed pottery and the evaporation cooled the butter and it was a convenient hygienic way to keep it.

Butter bells disappeared when ice boxes and refrigeration became common about 70 years ago but they have now been resurrected and can be purchased on line in several places for example at Amazon.  Unfortunately the concept of cooling by evaporation has been lost in the new ones that have glazed pottery bases so the butter is not chilled to the same extent.  However, apparently they still keep the butter cool but spreadable even in very hot summer weather. if the water is changed every 3 or 4 days, you can store butter in the bell for up to 30 days or more. 

Another unusual kitchen item that every good cook would probably appreciate is the ‘salt pig’ pictured on the right.  They are particularly convenient when you just want to add a pinch of salt or, if more, a small wooden spoon is available.  In the summer when there is lots of moisture in the air, be sure to mix a half teaspoon or so of rice with the salt to absorb water and keep it from caking.  They are available also at Amazon and other sites on line. 

Happy shopping!   Rie