Talk:Wetting

-DavidWeekly

"Physical Forces"
The High-energy vs. low-energy surfaces section states that weakly bonded molecules are: "held together essentially by physical forces (e.g., van der Waals and hydrogen bonds)." All particles that are held together are held together by physical forces, and everything in the universe that happens, happens because of physical forces. I think they mean physical bonds, which is a poorly defined, and in my opinion, misleading term used by some chemists as a synonym for "intermolecular bonds." I will change the word and link it to the article on intermolecular bonds.

Complete Wetting?
The High-energy vs. low-energy surfaces section states: "Most molecular liquids achieve complete wetting with high-energy surfaces." I will leave this in place because I don't have any articles to back up my intuition, but hasn't everyone here seen water bead up on a piece of glass or metal? This doesn't seem correct, and I suspect that this is a mistake and the opposite was meant.

Potentially off-topic
The High-energy vs. low-energy surfaces/Wetting of low-energy surfaces section states: "William Zisman had several key findings in the work that he did:[7] Zisman observed that cos θ increases linearly as the surface tension (γLV) of the liquid decreased. Thus, he was able to establish a rectilinear relation between cos θ and the surface tension (γLV) for various organic liquids. A surface is more wettable when γLV is low and when θ is low. He termed the intercept of these lines when the cos θ = 1, as the critical surface tension (γc) of that surface. This critical surface tension is an important parameter because it is a characteristic of only the solid."

This looks like good information, but the findings are not clearly related to the wetting of low energy surfaces. It is unclear if these findings are only true for liquids on low energy surfaces. If the relationship between cos θ and surface tension (γLV) of the liquid is only linear for low energy surfaces, this should be stated. If the relationship is linear for interfaces between liquids and high energy surfaces as well, this information should be moved to another section.

"Poorer" packing?
The High-energy vs. low-energy surfaces/Wetting of low-energy surfaces section states: "Differences in wettability between surfaces that are similar in structure are due to differences in packing of the atoms. For instance, if a surface has branched chains, it will have poorer packing than a surface with straight chains." Do they mean poorer wetting? The second sentence doesn't relate to the first, and I'm not sure what poorer packing would even mean as molecular packing is not a quantifiable unless some judgement criteria has been specified (ie, uniformity, density, degree of conformance to a particular crystal structure, etc.)

Cold welding
Would it be safe to say that wetting is a liquid equivalent of cold welding in that both occur when the surface of one material bonds to that of the other chemically rather than simply being pressed next to eachother? &mdash;BenFrantzDale 17:08, 5 December 2005 (UTC)

Cassie's law
I think Cassie's law as listed is incorrect. It should be either: $$\cos\,{\theta^*}= \phi \,\,cos\,(\theta_\text{Y} + 1)-1$$ or $$\cos\,{\theta^*}= r\,\,cos\,(\theta_\text{Y})-f$$

Needs editing
citing: "If the surface is high energy, it will want to be covered with a liquid because this interface will lower its energy, and so on."

As for the first clause, what does this mean - "If the surface is high energy". Furthermore, how does this follow: "... it will want to be covered with a liquid because..."? Since when do surfaces have minds of their own? How does a surface want something?

Re: Needs editing
It is common to say that any object "wants" something if it lowers it's energy. Objects do not have minds, but that's just a simple way of expressing the effect of lowering enery.

Ivopeters 08:24, 24 May 2007 (UTC)

Re: Needs editing
Given that the contact angle is the angle between the tangent to the surface of the liquid at the point where all three phases meet and the surface of the solid (as denoted by $$\theta_c$$ in Figure 4 of the article). I'm a little confused by the following excerpt from the article:

When a contact line advances, covering more of the surface with liquid, the contact angle is increased...A receding interface likewise has a contact angle that is reduced...

Wouldn't the contact angle decrease as the contact line advances, and the contact angle increase as the contact line recedes? Currently, I don't have access to the referenced material, so I can't check for the explanation.

--Jgrunschel (talk) 07:05, 21 January 2008 (UTC)

How does glass get completely wet ?
"There are two main types of solid surfaces with which liquids can interact. Traditionally, solid surfaces have been divided into high energy solids and low energy types. The relative energy of a solid has to do with the bulk nature of the solid itself. Solids such as metals, glasses, and ceramics are known as 'hard solids' because the chemical bonds that hold them together (e.g. covalent, ionic, or metallic) are very strong. Thus, it takes a large input of energy to break these solids so they are termed “high energy.” Most molecular liquids achieve complete wetting with high-energy surfaces."

Could someone please briefly explain (and possibly re-phrase) that last sentence to me ? It seems to say that if water, say, is poured on to a 'hard-solid' like glass, the glass will become completely wet. Which can't be right. Help ! Gnu Ordure (talk) 16:48, 5 February 2009 (UTC)

"Is water wet" debate
Could we possibly add a "In popular culture" section for the mention of the water wetness debate? Dragon Curve (talk) 02:21, 1 October 2020 (UTC)

Discussion on Jasper-Anand section
The user Nadish21 appears to be using this page as a vehicle to promote his own scientific work. The equations from the Jasper-Anand paper were added to Wikipedia within 10 days of its publication. Unknown users have repeatedly rolled back the efforts of others to remove the section from the page.

Although the publication is peer reviewed, it is really questionable to list it as an important result in a field that is at least a century old. As a researcher in this field I find the paper to be of poor quality and there are many other well regarded papers that far deserve to be mentioned on this page (to give one example: 10.1063/1.1563828). — Preceding unsigned comment added by 103.6.151.208 (talk) 30 May 2021

Reply: The justification for removing this section does a disservice to the field of wetting for the following reasons: 1. The Young-Dupre equation, which has been a well established theory for over two centuries, also happens to be incompatible with the First Law of Thermodynamics. 2. Existing theories such as the Young-Dupre equation or the Modified Young's Equation do not agree with peer reviewed experimental data on predicting the contact angle of small sessile droplets. 3. Existing theories predict incorrectly the magnitude and sign of the line tension term. 4. The Young-Dupre equation fails to predict contact angle hysteresis for sessile droplets.

In contrast, the section which is being proposed to be deleted: 1. Agrees with the First Law of Thermodynamics. 2. Agrees with experimental results over 14 orders of magnitude in droplet volume. 3. Correctly predicts the sign and magnitude of the line tension term at the three phase boundary. 4. Correctly predicts contact line hysteresis.

Instead of self-censoring this section, would it not be more prudent for the readers to decide for themselves between theories which do not agree with experiment and those that do? Finally, passing on conjecture and one's opinions, without hard scientific evidence that disproves this particular theory, should not be the basis for censoring this section. — Preceding unsigned comment added by 2600:1700:B01:5880:20C2:CA26:3A59:B101 (talk) 22:24, 23 January 2022 (UTC)

More self-promotion on "A Generalized Model for the Contact Angle of Droplets on Flat and curved surfaces"
Some months ago I wrote ("Discussion on Jasper-Anand section") that a user was seemingly promoting his own academic work, adding equations from a paper days after its publication.

Someone has continued to surreptitiously add the work of Jasper and Anand to this Wikipedia page, now in a section titled "A Generalized Model for the Contact Angle of Droplets on Flat and curved surfaces". Apart from what seems to be a shameless act of self-promotion from someone who calls himself the progenitor of the Jasper-Anand equation), there is no really compelling reason why this paper should be featured over papers from more established names in wetting such as Tadmor, Extrand and so forth.

In an earlier comment an unsigned commenter claims that Jasper and Anand's theory agrees with experimental results over 14 orders of magnitude and correctly predicts the sign and magnitude of line tension. These claims are wrong because the order of magnitude of the line tension is a notoriously unsolved problem (see B M Law et al https://spiral.imperial.ac.uk/bitstream/10044/1/53476/6/Line%20tension%20Prog%20Surf%20Sci%20Submission%20BMLaw%20082016.pdf) whose experimental measurements notably conflict with one another. 103.252.202.193 (talk) 06:41, 14 February 2023 (UTC)