# Do rinse agents actually deposit something on the dishes? **URL:** \ **Category:** Factual Questions\ **Created:** [September 1, 2016, 4:10pm UTC](https://boards.straightdope.com/t/do-rinse-agents-actually-deposit-something-on-the-dishes/764669 "2016-09-01T16:10:31Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![CC](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@CC](https://boards.straightdope.com/u/CC)\ **Post date:** [September 1, 2016, 4:10pm UTC](https://boards.straightdope.com/t/do-rinse-agents-actually-deposit-something-on-the-dishes/764669/1 "2016-09-01T16:10:31Z")
Just bought a new dishwasher, and I see (on a website about dishwashers - sponsored by Finish) that one of the components of the materials used to clean dishes is called a rinse agent. They say “Polymers help create the shine.” This seems to say that there is something (polymers) deposited onto the glassware in the process of cleaning them. Does this mean that the impression of cleanliness imparted by the shine of freshly washed dishes is in reality the result of having a thin layer of shiny polymers covering the glass? Inquiring minds want to know. (This is the kind of thing Cecil used to relish exploring.) ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [September 1, 2016, 4:20pm UTC](https://boards.straightdope.com/t/do-rinse-agents-actually-deposit-something-on-the-dishes/764669/2 "2016-09-01T16:20:06Z")
Proctor and Gamble’s [patent](https://www.google.com/patents/EP1102834B1?cl=en) includes this: > [@](#): > > Rinse aids are used in commercial and institutional machine dishwashers and very often, also in household automatic dishwashers. During the rinse cycle, a final rinse of fresh water serves to displace pre-final rinse water and its attendant detergent and soil residues. Rinse aid formulations are aqueous solutions containing a low foam nonionic surfactant. During the rinse cycle, the rinse aid is injected into the final fresh water rinse at a concentration of about 100 to about 500 ppm. The surfactant in the rinse water lowers the surface tension of the rinse water and improves the wetting action of the rinse water on the somewhat hydrophobic substrate surfaces. Improved wetting reduces the tendency of the rinse water to form drops containing dissolved solids on the substrate surface which give rise to spots upon drying. Accordingly, the functions of the surfactant in the rinse aid are to effectively reduce the surface tension during the draining period and to be low foaming so as to avoid traces of foam on the rinsed substrate which result in a residue upon evaporation. While low foam surfactants have improved the wetting of rinse water on substrates, they have not completely eliminated spotting and streaking problems. It is known that the addition of a low molecular weight neutralized polyelectrolyte, such as polyacrylate, to the rinse water can further reduce spotting and filming or streaking. ---
**Author:** ![CC](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@CC](https://boards.straightdope.com/u/CC)\ **Post date:** [September 1, 2016, 4:57pm UTC](https://boards.straightdope.com/t/do-rinse-agents-actually-deposit-something-on-the-dishes/764669/3 "2016-09-01T16:57:30Z")
This doesn’t really explain the mechanism by which the polyacrylate reduces spotting or streaking. Is it because it further diminishes the water’s ability to cohere into drops and stick to the surface of the glass? or is it because it creates a film on the glassware that water does not adhere to? I can’t tell by reading the patent information. (Which is one of the several reasons that I’m not a patent attorney.) ---
**Author:** ![Kent\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kent_clark/32/105_2.png) [@Kent\_Clark](https://boards.straightdope.com/u/Kent_Clark)\ **Post date:** [September 1, 2016, 9:31pm UTC](https://boards.straightdope.com/t/do-rinse-agents-actually-deposit-something-on-the-dishes/764669/4 "2016-09-01T21:31:51Z")
[A rinse agent is a surfactant](http://www.treehugger.com/cleaning-organizing/what-dishwasher-rinse-aid.html). Its particular action is to prevent water from forming little droplets that dry into water spots, instead keeping the water in sheet form that runs off the dishes more easily and lets them dry spot-free. While I think the article I linked to is unecessarily scary, at least it notes that some surfactants are relatively harmless. ---
**Author:** ![CC](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@CC](https://boards.straightdope.com/u/CC)\ **Post date:** [September 2, 2016, 1:52am UTC](https://boards.straightdope.com/t/do-rinse-agents-actually-deposit-something-on-the-dishes/764669/5 "2016-09-02T01:52:06Z")
Yeah - my concern is not a health-related one. I’m wondering if the shine that they’re promoting comes from effectively getting the water to evaporate or drain without leaving any dissolved residue, or if it’s from a very thin layer of polymer that makes the glass shiny. One way seems more honest than the other.