Welcome back. I’ve been doing a little doodling this week. Okay, colouring. I guess I am just a kid at heart… back to the crayons. Actually, they were markers and coloured pencils. Are there any artists out there? Colouring is a great art form; some of us are better at it than others. I happened to pick up a beautiful set of pastel pencil crayons some time ago, thrifted, of course. And yet, I haven’t mastered the art of using them. And hence, this week’s muse: chalk. Pastels are a form of chalk.
Most of we’re probably exposed to blackboard chalk back in elementary school. Cleaning all those dusty brushes and hacking up a lung. Kids these days have it easy: their chalk is “dustless”. What am I saying? Whiteboards and computer screens have replaced all those items now. Chalkboards are reduced to upscale coffee cafes and artists who know how to use pastels. Technically the artist’s medium is not chalk (calcium carbonate) but a form of gypsum these days. Lucky for us, gypsum is less dusty.
Wanna delve into the technical? Here ya go: chalk and gypsum have both been mined since ancient times. Chalk has been found in cave paintings that date way back, while gypsum (calcium sulphate) has been used as a mortar for construction since, like, forever, and is even found in the Egyptian pyramids.
Similar and yet distinct, chalk is a base (an alkaline that neutralizes acids) that is composed of calcium and oxygen combined with carbon (CaCO3). At the same time, gypsum is a salt (the product of a base and acid reacting and both becoming neutralized), made up of calcium and oxygen combined with sulphur.
Both are believed to be formed in a similar fashion. Chalk is a limestone deposit created as plankton (tiny marine organisms) concentrate calcium in their bodies while living, then leach the calcium out after they die and settle onto ocean floors; over time, large deposits are formed, and as the seas recede, chalk “mountains” are built up for our collection.
Gypsum’s origins are similar, but in addition to being comprised of the calcium produced by the deaths of millions of plankton, gypsum also contains some of the salt left behind as the ocean evaporated. Salty chalk.
After quarrying, each material is crushed, ground, washed and sifted. With gypsum, it must also be dehydrated in a process that involves high temperatures to reduce its water content from nearly 21% to about 5-6%; for that non-dusty classroom chalk, the material is mixed, again, with water (and coloured pigments, if desired; note most common chalk is green nowadays) and to produce more exotic pastels like my thrifted treasure, pigments as well as clays or oils are also added. For the former, the chalk is baked, while for the latter, it is air-dried.
Brain hurting yet? Thanks to todayifoundout.com for all that info.
I love how God gives us renewable products for our use. Nature is cool. Who would have thought dead sea creatures could make art… or hold our houses together? He celebrates our creativity as His beloved creations! Who else can boast that our “creations” are creative??
Wanna hear one more cool fact about chalk? Apparently, around Christmas, there is a tradition known as “chalking the door” where marks are chalked across the door of a home as a reminder that the Wisemen came to visit and worship the young Jesus — and we should do likewise when we enter other people’s abodes. It’s placed on the door frames to remind those who enter, that our homes are places of spiritual growth, and dedication to faith, and that we should be a blessing to all who enter! Chalk that one up my friends!
Chromatography, in its simplest terms, means “separating parts of a mixture”. Scientists do this for all kinds of mixtures: gases, liquids and solids can all be separated into their various parts. For example, blood can be separated out to search for specific diseases. Oil companies often use chromatography to weed out impurities in their products. Gases can be diffused and distilled to investigate all about bombs and warfare. Distillation is closely related to chromatography and is another method for separating mixtures. Perhaps you can investigate the differences! For our example, we are going to be using paper chromatography to separate liquid pigments (in markers) into their various colours. Pigments are also found in other everyday objects like leaves and candy… even more to investigate!
mittonmusings 