# How to know how much heated water has evaporated during lotion manufacturing?

Member
Is there any theory or way to calculate how much water has evaporated during lotion manufacturing if the work temperature is above 60°c?

How do you guys calculate yours?

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• Member
The batches are 50kg and 200kg.

To find the evaporation rate of water i did an experiment. I heated 200g water to 60°c. After 5 minutes the temperature dropped to 57°c and 2g water evaporated.

Is this the correct way to evaluate?
• Member, Professional formulator
edited August 2021
You need to determine this yourself.
• Member
@PhilGeis hahaha yeah but knowing how you guys are doing it would help me a lot.

I did the experiment on 200g water to find the evaporation rate of water but at 200kg the evaporation rate is far less than 1% at 5 minutes. So this was not helpful 😃
The answer is going to depend on too many factors to make it easy to calculate.  Mixing speed, surface area, surface temperature, composition of formula, atmospheric humidity, etc.

You'll have to make a big batch 200kg and weigh it before and after.  Do that about 30 times and you'll get an answer that reflects the normal distribution of the process.
• Member, Professional formulator
"Yield" what you get out of your production - as Perry said, is fairly unique to formula and process.
• Member
Only way is to make a batch...and weigh in and weigh out.  Too many factors....from time it takes to reach temp...surface area involved, relative humidity...and the list goes on....and on.  Example....if you heat a small batch quickly in the microwave...it will lose FAR less water than the same batch heated more slowly on a lab plate.
• Member, Professional Chemist
if you keep your vessels closed when not adding materials, and minimise the size of the head space above the surface of the batch, water loss will be proportionately very low, especially when compared to the lab scale
UK based formulation chemist. Strongest subjects: hair styling, hair bleaches, hair dyes (oxidative and non-oxidative) I know some stuff about: EU regulations, emulsions (O/W and W/O), toothpaste, mouthwash, shampoos, other toiletries
• Member
@Graillotion for up to 10kgs batch that is the way but for 50kg and 200 kg I don't know how to weight it. Do you know any device fot that?

Also for 50kg and above i use inline homogenizer so some of them  would be inside the pipe, although can fill the pipe and check how much material fits there.

Another problem is the evaporation rate is different for different sizes.
For smaller batches the evaporation rate is higher than large batches so I can't guess it from measuring it.
• Member
@Bill_Toge thanks. That looks like a good idea.
• Member, Professional Chemist
put it another way: the amount of heat energy in a given batch is governed by how much volume there is in that batch, and the material loss from that batch by evaporation is governed by how much of the batch's surface area is open to the atmosphere
assuming your batch is roughly hemispherical, as per standard reactor designs, then the volume is proportional to the radius of the vessel cubed, while the surface area exposed to the air proportional to the radius of the vessel squared; as the size of the vessel increases, the amount of surface area per unit volume decreases, and the so the amount of water loss decreases too
UK based formulation chemist. Strongest subjects: hair styling, hair bleaches, hair dyes (oxidative and non-oxidative) I know some stuff about: EU regulations, emulsions (O/W and W/O), toothpaste, mouthwash, shampoos, other toiletries
• Member
@Bill_Toge thanks