dye vat = ski resort?
I said i'd write a post on my new favorite analogy: how vat-dyeing fabric is like a ski resort, which i came up with on the fly recently while helping a student with a class project.
The question was, how come sometimes you put fabric into a dye bath and after a given period of time, it stops getting darker, but the bath is still the color of the dye? And, how sometimes when you add more dyestuff to that bath, the fabric will get even darker when you reintroduce it to the bath, though it had previously seemed like it was as dark as it was going to go?
Here's the analogy:
The dye process itself is the lift line at a ski resort, where the vat bath is the resort. Dye molecules are like skiers, and the fibers of the fabric are like a ski lift. Of all the skiers at the resort, some will be in line to get on the lift; as long as there is an open bench, they can get on. Not all the skiers will want to be on the lift at the same time though. Some may never get in line--these are the dye molecules that just hang out in the bath. At a certain point, the lift line is empty. No more skiers care to get on the lift, though some may be still whizzing down hills. If you add more dye concentrate--skiers--then the lift line will form again and more skiers will resume getting on lift benches.
Of course, this analogy *totally* breaks down when the lift gets to the top of the hill and disgorges skiers, since in a dye process, you usually need some sort of discharging agent to release dye molecules from dye sites. So i guess at the end of the lift is a giant bucket of bleach. Or something.
Hey, it seemed to make more sense than talking about chemistry at that point in the day.
The question was, how come sometimes you put fabric into a dye bath and after a given period of time, it stops getting darker, but the bath is still the color of the dye? And, how sometimes when you add more dyestuff to that bath, the fabric will get even darker when you reintroduce it to the bath, though it had previously seemed like it was as dark as it was going to go?
Here's the analogy:
The dye process itself is the lift line at a ski resort, where the vat bath is the resort. Dye molecules are like skiers, and the fibers of the fabric are like a ski lift. Of all the skiers at the resort, some will be in line to get on the lift; as long as there is an open bench, they can get on. Not all the skiers will want to be on the lift at the same time though. Some may never get in line--these are the dye molecules that just hang out in the bath. At a certain point, the lift line is empty. No more skiers care to get on the lift, though some may be still whizzing down hills. If you add more dye concentrate--skiers--then the lift line will form again and more skiers will resume getting on lift benches.
Of course, this analogy *totally* breaks down when the lift gets to the top of the hill and disgorges skiers, since in a dye process, you usually need some sort of discharging agent to release dye molecules from dye sites. So i guess at the end of the lift is a giant bucket of bleach. Or something.
Hey, it seemed to make more sense than talking about chemistry at that point in the day.