In Oliver's video 028 on Vitamin C under polarization, he shows heat drying the slide. On the Facebook Amateur Microscopy group, I see references to heat drying. I know how, but I don't know when.
I experiment by mixing various substances/chemicals but I don't know when heat drying is appropriate.
Guidance, please.
Maryfox
Heat Drying
Re: Heat Drying
Until someone that often experiments with crystallization polarization microscopy responds, here is a rule of thumb:
If the salt or whatever chemical you put on the slide is dissolved in water, evaporation is relatively slow. In that case, every about 10C rise of the temperature above ambient (say, 35C when room temp is 25C) will double the rate of drying. This holds while most of the water is still there - at the beginning of the experiment. At a later stage, as the surface area of the solution drop is diminished, the rate of drying is accelerated even more.
If the salt or whatever chemical is dissolved in alcohol (IPA, ethanol - not methanol), "drying" (more appropriately, evaporation) much faster than if it is dissolved in water - roughly 3 times as fast. If it is dissolved in acetone or methanol - roughly 10 times faster than in water (all comparisons hold for the same temperature). The effect of temperature on the rate of drying is identical to the effect on water drying, however.
Usually, the beautiful polarization color patterns develop gradually upon drying, so I would always start without heat - just let dry at room temperature, and heat a little if necessary.
If the salt or whatever chemical you put on the slide is dissolved in water, evaporation is relatively slow. In that case, every about 10C rise of the temperature above ambient (say, 35C when room temp is 25C) will double the rate of drying. This holds while most of the water is still there - at the beginning of the experiment. At a later stage, as the surface area of the solution drop is diminished, the rate of drying is accelerated even more.
If the salt or whatever chemical is dissolved in alcohol (IPA, ethanol - not methanol), "drying" (more appropriately, evaporation) much faster than if it is dissolved in water - roughly 3 times as fast. If it is dissolved in acetone or methanol - roughly 10 times faster than in water (all comparisons hold for the same temperature). The effect of temperature on the rate of drying is identical to the effect on water drying, however.
Usually, the beautiful polarization color patterns develop gradually upon drying, so I would always start without heat - just let dry at room temperature, and heat a little if necessary.
Re: Heat Drying
There is also a "Why": By heating you can influence the crystallisation process.
Re: Heat Drying
Thanks for your replies. I've gotten some very interesting polarized images with just air drying but I was wondering if there was some Magic to heat drying. You've answered my question.