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# Physics/calculating surface tension

Question
Hello Steve,

I want to deposit some electrically conductive paste onto a flat substrate. After depositing the paste, this substrate will be turned upside down, and I would like to try to calculate whether the paste is likely to fall off.
The paste is made up of a fine metal powder in a viscous gel. I can get information on the weight and viscosity of the paste, but I am not exactly sure where to go next. My thinking is that the weight of the paste deposit needs to be less than the surface tension, but I don't know how to calculate surface tension, and the info online seems to be for different scenarios (eg water drops falling from a pipe).
Can you give me some advice on how to calculate the surface tension holding a viscous material to a flat surface when turned upside down?

Thanks in advance, and apologies in advance if I have described something unclearly!
Best regards,
Eddie

Hello Eddie,

This is not a specialty of mine so I have had to search for related material. Use these links and see how well they apply. Notice that the first and second disagree regarding the existence of a relation between surface tension and viscosity. The 3rd adds the idea of adhesion to consider. Notice the conditions (vibration for example) that are mentioned that interfere with these factors.
http://www.cscscientific.com/csc-cientific-blog/bid/52996/How-Does-Surface-Tensi
http://pubs.acs.org/doi/abs/10.1021/je60035a016?journalCode=jceaax
http://www.mikeblaber.org/oldwine/chm1045/notes/Forces/Liquids/Forces03.htm

I hope this helps,
Steve
Questioner's Rating
 Rating(1-10) Knowledgeability = 10 Clarity of Response = 10 Politeness = 10 Comment Thanks Steve, I always appreciate your help!

Physics

Volunteer

#### Steve Johnson

##### Expertise

I would be delighted to help with questions up through the first year of college Physics. Particularly Electricity, Electronics and Newtonian Mechanics (motion, acceleration etc.). I decline questions on relativity and Atomic Physics. I also could discuss the Space Shuttle and space flight in general.

##### Experience

I have a BS in Physics and an MS in Electrical Engineering. I am retired now. My professional career was in Electrical Engineering with considerable time spent working with accelerometers, gyroscopes and flight dynamics (Physics related topics) while working on the Space Shuttle. I gave formal classroom lessons to technical co-workers periodically over a several year period.

Education/Credentials
BS Physics, North Dakota State University
MS Electrical Engineering, North Dakota State University