Water Beading - http://togwt1980.blogspot.co.uk/2017/11/does-water-breading-equate-to-paint.html
Beading is a surface interaction between water and the paint surface; dust or dirt particulates, oxidation, environmental pollutants, and etc. interfere with the surface tension, thereby disrupting the beading. Beading that is left to evaporate on a car will lead to water marks; if there is acid or alkali contamination in the water.
Dependent upon the water source; clean rainwater has no harmful effects; but cognizant that water beading whatever its aesthetic value doesn’t equate to surface protection. The average unprotected water-based paint absorbs approximately a pint of water; dependent upon what’s in the water this may be harmful.
Pros: the aesthetics of water beading are sought after by many detailers. Many detailers believe that if there is water beading on a paint surface the LSP is providing protection. Nothing could be further from the truth; water beading is primarily due to surface tension
But if a product beads on initial application and after a period of time starts to sheet water (or vice-versa) it is normally indicative that the wax/sealant protection has diminished.
Cons: dependent upon the water source clean rainwater has no harmful effects, acid rain is inert until heat is added and then it become corrosive, the water from a standard household supply usually contains minerals like calcium (Ca) magnesium (Mg) and alkaline. The beads have a very small surface area, so the sun will increase the surface temperature very rapidly once these form reactivity starts (moisture, heat and an acid or alkaline) and once they are dried they will cause etching (a shallow indentation) of the paint surface
Be cognizant that (a) Dust and road soil will also have a negative impact on water beading this is often mistaken as paint protection product failure. (b) Durability can fluctuate dependent upon environmental conditions and the products used between the application of a wax/sealant and the use of quick detailers (QD), car wash concentrate that contains a wax, spray wax, etc)
Does water beading equate to durability or to actual surface protection?
Beading is a surface interaction between water and the paint surface, both a protected or just a clean painted surface. Dust or dirt particulates, oxidation, environmental pollutants, and etc interfere with the surface tension, thereby disrupting the beading
Most waxes/paint protection will bead until enough surface tension is created, and then it will sheet as the volume of water increases. Beading of rain water on the surface of a waxy surface, such as an automobile is due to surface tension. Water adheres weakly to wax and strongly to itself, so water clusters into drops. Surface tension gives them their near-spherical shape, because a sphere has the smallest possible surface area to volume ratio.
Nearly all wax and sealant products exhibit water beading or sheeting initially (in fact so does a clean paint surface without an applied protection) this is due solely to surface tension, once the protection breaks down (abrasion from water, road dirt/grime and other airborne pollutants) it will cause a reduction in the surface tension and the beading will revert to its former level
Slickness is also not an indicator of protection; as it comes from the (silicone) polymers and oils, once applied and exposed to the environment they start to evaporate / deteriorate. If your goal is maximum protection, don`t use water beading/sheeting as an indicator; while itâ€™s true that it is a visual indicator that a wax / sealant previously applied is still present it does not guarantee that itâ€™s actually providing protection.
Hydrophobic beading on a paint surface is aesthetically pleasant, and many people equate beading with protection; there is a long standing myth- that as long as a paint surface maintains beading it’s being protected from the elements (much like the myth that the more soap produces suds the better the cleaning effect) There are many things that will affect the shape of a water bead on a surface; since gravity, surface tension and the surface energy of the coating all play a part.
To test your paint protection you must measure the water beading of your paint (height, contact angle and diameter) without any polish/wax applied. Next, measure the water beading of your paint (height, contact angle and diameter) within 24 hours after initially applying your polish/wax.
This is your starting point. This will also be the gauge for determining the water beading (longevity, duration and changes) for that specific product. As the water beads start to diminish (get wider and shallower and loses contact angle), the polish/wax and its film protection factor is going away, Once the water beading is the same as before you apply your product, the polish/wax and its protection are gone
Dust and road grime will have a very negative effect on surface beading than any other factor. The effect of this is often misconstrued as wax failure when this isn`t the case.
Durability [: able to exist for a long time without significant deterioration] varies depending on various environmental factors, including but not limited to:
Product is applied to a clean, cool and dry surface
Product was allowed to cross-link and form a molecular bond with the paint system
No oils or water (including moisture, dew, etc) was introduced to the surface before it has formed a molecular bond
What the environmental conditions (ambient temperature etc) are where the vehicle is stored
The kind of airborne contaminants the vehicle is regularly exposed to
Frequency of washing and kind of car wash solution used (i.e. detergent strength, etc)
[: convex beads that have a small, tight symmetrical shape due to cohesion]
Although you cannot equate a products beading ability to protection and durability, if an applied product continues to `bead` water, one wash after another, then that would prove that whatever it is that is causing high surface tension is not washing off.
How can you tell when a paint surface protection has diminished to a point that it is no longer being protected?
Water (H2O) is a polar molecule, composed of two hydrogen's (H2) atoms bonded to a single oxygen (O2) atom. Water molecules adhere to each other, this is called cohesion.
Water molecules also can be attracted to other substances, such as metal or dirt, especially if they have some static charge on them, this is called adhesion.
Some substances are not attracted to water and even repel it. These include oils, fats and waxes; these are called non-polar substances.
When water falls on a surface where no oils are present, the forces of adhesion and cohesion are almost in equilibrium, and the water spreads out
A wax or sealant, when applied properly to a clean paint surface, fills in the larger surface fissures and layers the whole surface. The chemical structure of the wax prevents water from penetrating to the surface of the car. Because the wax itself is hydrophobic (literally repels water), the forces of adhesion are much less than the forces of cohesion. So, water is more likely to bead higher and rounder than on a surface without wax/sealant
a) If the paint surface feels dry (your hand or a towel meets resistance), it’s an indication that there’s nothing left between you and the paint finish. Glazes, waxes and polymer’ create a finish with less friction (surface tension) than the paint itself.
b) A suggestion from a polymer product manufacturer Sal Zaino - To test your wax/sealant you must measure the water beading of your paint (height, contact angle and diameter) without any polish/wax applied.
Next, measure the water beading on your paint (height, contact angle and diameter) within 24 hours after initially applying your polish/wax. This is your starting point. This will also be the gauge for determining the water beading (longevity, duration and changes) for that specific product.
As the water beads start to diminish (get wider and shallower with a diminished s contact angle), the polish/wax and its film protection factor is going away, Once the water beading is the same as before you apply your product, the polish/wax and its protection are gone
Conclusion- water beading is indicative but not conclusive proof of protection
The hydrogen bond between water molecules is the reason behind two of water's unique properties: cohesion and adhesion. Cohesion refers to the fact that water sticks to itself very easily. Adhesion means that water also sticks very well to other things, which is why it spreads out in a thin film on certain surfaces, like glass. When water comes into contact with these surfaces, the adhesive forces are stronger than the cohesive forces. Instead of sticking together in a ball, it spreads out.
Surface tension is a property of the liquid and not of the surface. This means that the molecules on the surface of the water are not surrounded by similar molecules on all sides, so they're being pulled only by cohesion from other molecules deep inside. These molecules cohere to each other strongly but adhere to the other medium weakly.
Water beading is created due to a high surface tension on the vehicle. The higher the surface tension, the smaller and tighter the formation of the beading will be. The lower the surface tension, the bigger the beads will be. Surface tension is the ability of a liquid to adhere to its neighbouring water molecules. Once the surface water beading changes shape (from the initial small tight beads to a lager ‘flat’ bead or the water sheeting becomes much ‘slower’ the painted surface is losing its tension.
There are however exceptions: a freshly painted surface will bead with no wax or sealant on it and a just-polished vehicle will also bead with no wax or sealant. This is due to the oils that are present, that promote beading.
Changes to the surface tension
The water tension changes throughout the life cycle of the surface protection and maybe a more indicative indicator of the performance. Indications that the products durability may be diminishing- (contact angle varies) when the water beads become noticeably larger in diameter with a flat, concave or an irregular shape usually indicate that the surface tension of the wax or sealant is diminishing. Or when dust, dirt or bug residue becomes more difficult to wipe off with a quick detailing spray are indications that it may be time to renew the protection
It could be something as simple as a dirty surface or contamination, which increases the surface area. If the surface is clean then `something` on the surface itself has changed. In terms of a wax or sealant, this likely means that some of the protective film (the part that reduced the attraction of water) is gone. This could suggest that the paint protection product is beginning to lose its effectiveness.
d) Slickness- slide a micro fibre towel across a horizontal surface to see how much resistance there is, if there has been a significant reduction from what you experienced previously the durability is probably diminishing
e) Sheeting (hydrophilic) - the self cleaning (sheeting) ability of the hydrophilic polymer seems to be much better than the hydrophobic organic wax (beading) effect, as it may accelerate the oxidation when drying after rain.
There are some disadvantages to water beading (hydrophobic) as opposed to the sheeting effect (hydrophilic) of a polymer, when they are dried by ambient temperature they cause water spots (if the rain contains calcium it will leave a white residue) The other is there could be over a pint of liquid trapped within the beads over the paint film surface area, if they contain acid from industrial fall out (IFO) this could increase the time the acidic solution remains on the paint surface compared to water sheeting
The beads have a very small surface area, so the sun will increase the surface temperature very rapidly; many chemical compounds react to slight heating and an oxidizing process. Now you have acid + water + oxygen + ozone + heat; all of which equates to reactivity, which produces a highly concentrated acidic solution, causing concave indentations (acid etching) to the paint surface
Any product can be reformulated with active surface agents (surfactants) either ionic (sheeting) or non-ionic (beading) that alters the surface tension and causes water to sheet or bead to satisfy consumer demand.
But if a product beads on initial application and after a period of time starts to sheet water (or vice-versa) it is normally indicates that the wax/sealant protection has diminished.
The beads sitting on the surface can cause spotting or etching, whether in the coating or the paint. If there are contaminants in the water like acid rain or other stuff, it can work its way to etch all the way to the paint.
We have established that both surface energy and contact angle are crucial to the efficiency of a paint protection product (ignore surface pencil hardness as they are a very minor factor) Determining the surface energy can be achieved by measuring contact angle or by use of Surface Energy Test Liquids or Pens (Dyne level testing).
This form of measurement is based on the ISO method for measuring the surface energy. Surface energy may be defined as the excess energy at the surface of a material compared to the bulk. Every solid surface has a specific and measurable surface energy.
The unit of measurement used is the Dyne/cm² or mN/m.
When the Dyne level test liquid is applied to the surface, the liquid will either form a continuous film on the surface or pull back into small droplets.surface or pull back into small droplets. If the Dyne test fluid remains as a film for 3 seconds, the substrate will have a minimum surface energy of that Dyne Pen liquid value (Dyne Test Pen fluids are available in values from 30 to 70 mN/m. Should the Dyne test liquid reticulate or draw back into droplets in less than 1 second then the surface energy of the substrate is lower than that of the Dyne Test Pen liquid itself.
The exact surface energy (Dyne level) can be determined by applying a range of increasing or decreasing values of Dyne test pens.
To test the viability of a coating requires measuring the surface energy (surface tension).
One of the first steps to ensure a paint coatings viability is to determine the dyne level. Dyne Marker pens can be used to measure the surface energy of coatings and films and other non-absorptive substrates, this method parallels ASTM Std. D25781
A Dyne marker pen is an accurate tool to measure the surface tension level or Wetting Tension of a paint protection coating surfaces. There are different ranges of dyne kits based on your requirements covering the specified range of dyne levels in two dyne increments.
In general, the ability of a substrate to anchor a coating, or adhesives is directly related to its surface energy. If the substrate surface energy does not significantly exceed the surface tension of the fluid which is to cover it, wetting will be impeded and a poor bond will result. Thus, for most paint protection coatings need to be treated to 36 to 40 dynes/cm (see Note 1)
For the results of this test to be meaningful, the following four points are absolutely essential and must be followed:
a) Do not touch or in any way contaminate the surface to be tested. Dirty surfaces lose their wettability.
b) Do not use contaminated or outdated marker pens.
c) Never retest the same location on a sample; move along the sample, or pull a new one.
d) Store and use marker pens at room temperature.
a) Pull test sample. Be sure to pull a good specimen; surface aberrations cause poor results. For an extruded film, one entire web cross-section should suffice. Do not touch the surface.
b) Place the sample on a clean, level surface. If necessary, anchor the edges to avoid curling or other deformation.
c) Record ambient temperature and relative humidity. If sample temperature differs from ambient, allow it to stabilize.
d) Test at least three points across the sample; 1/4, 1/2, and 3/4 across the film section. It is good practice to test the outer edges as well. For non-film materials, test locations must be determined in-house.
Determination of Wetting
1. Choose a marker pen at a dyne level you believe is slightly lower than that of the test sample.
2. Press applicator tip firmly down on subject material until the tip is saturated with ink.
3. Use a light touch to draw the pen across the test sample in two or three parallel passes. Disregard the first pass(es); to flush any contamination from the tip, and to ensure that the test fluid layer is thin enough for accurate measurement, evaluate only the last pass.
4. If the last ink swath remains wetted out on the test sample for three seconds or more, repeat steps 2 and 3 with the next higher dyne level marker. If the last ink swath beads up, tears apart, or shrinks into a thin line within one second or less, repeat steps 2 and 3 with the next lower dyne level marker. If the ink swath holds for one to three seconds before losing its integrity, the dyne level of the marker closely matches that of the sample.
Finally, a few qualifying words. Surface energy is critically important to many converting operations. Unfortunately, it is not the sole determinant of product suitability. Other factors, such as surface topography, coating rheology, and chemical incompatibility, must also be considered.
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