# Non-toxic reflective Liquids? **URL:** \ **Category:** Factual Questions\ **Created:** [March 22, 2013, 7:17pm UTC](https://boards.straightdope.com/t/non-toxic-reflective-liquids/653674 "2013-03-22T19:17:07Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![eltro102](https://avatars.discourse-cdn.com/v4/letter/e/7cd45c/32.png) [@eltro102](https://boards.straightdope.com/u/eltro102)\ **Post date:** [March 22, 2013, 7:17pm UTC](https://boards.straightdope.com/t/non-toxic-reflective-liquids/653674/1 "2013-03-22T19:17:07Z")
What reflective liquids are there? aside from our old friend mercury I know that gallium and some alloys of it are liquid but they have a very high viscosity, wouldn’t really work for my thing I remember reading a discussion on this on some astrophotography forum about using reflective liquid mirror (as they make parabolas when spun), but I can’t seem to dig it up again. The main reason I’m asking this is [HOURGLASS Filled with MERCURY - What HAPPENS? - YouTube](https://www.youtube.com/watch?v=1cGsm_eaNhw) I want to make something like that in the video but without the danger of the glass breaking and mercury flying everwhere ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [March 22, 2013, 8:42pm UTC](https://boards.straightdope.com/t/non-toxic-reflective-liquids/653674/2 "2013-03-22T20:42:58Z")
> **[Liquid-mirror telescope](https://en.wikipedia.org/wiki/Liquid_mirror_telescopes)** > > Liquid-mirror telescopes are telescopes with mirrors made with a reflective liquid. The most common liquid used is mercury, but other liquids will work as well (for example, low-melting point alloys of gallium). The liquid and its container are rotated at a constant speed around a vertical axis, which causes the surface of the liquid to assume a paraboloidal shape. This parabolic reflector can serve as the primary mirror of a reflecting telescope. The rotating liquid assumes the same surface shap... _Since mercury metal and its vapor are both toxic to humans and animals there remains a problem for its use in any telescope where it may affect its users and others in its area. The less toxic metal gallium may be used instead of mercury but has the disadvantage of high cost. Recently Canadian researchers have proposed the substitution of magnetically deformable liquid mirrors composed of a suspension of iron and silver nanoparticles in ethylene glycol. In addition to low toxicity and relatively low cost, such a mirror would have the advantage of being easily and rapidly deformable using variations of magnetic field strength.[3][4]_ I don’t don’t where to get silver nanoparticles suspended in ethylene glycol, though. Ferrofluid could work if you don’t need very high reflectivity. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [March 22, 2013, 8:44pm UTC](https://boards.straightdope.com/t/non-toxic-reflective-liquids/653674/3 "2013-03-22T20:44:54Z")
_All_ liquids are reflective liquids, within the limits of Fresnel reflection. So there are plenty of them, including the most common, water. I’m not being snide here – I’ve worked with reflections from liquids, including water. It may be low (very nearly 2% at a surface), but that’s sufficient for many applications. You could make a parabolic mirror by spinning a container of water. (In fact, some contact lens companies made the back surfaces of their soft contact lenses by spinning containers of the hydropolymer and curing it under UV light. But I wouldn’t drink those). Mercury is, as you say, toxic, but that doesn’t stop people from making parabolic mirrors of them. R.W. Wood made a parabolic mercury mirror, and other people have done it more recently: [http://wood.phy.ulaval.ca/index.php/Rotating\_Liquid\_Mirrors](http://wood.phy.ulaval.ca/index.php/Rotating_Liquid_Mirrors) Raymond Z. Gallun had a Martian astronomer use a mercury mirror in a story from back in the 1930s. I know of people who proposed liquid alkali metal mirrors for laser fusion purpooses. Those are pretty dangerous, too. You might want to try low temperature melting alloys, such as Galinor (liquid at room temperature) or other low temperature alloys. Galinor is supposed to be “sticky”, though. Depending upon how picky you are about things, you might be able to get what you want from a rotating liquid covered by a thin sheet of aluminized polymer, or liquid filled with bits of metal sheet or aluminized metal. ---
**Author:** ![TroutMan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/troutman/32/6721_2.png) [@TroutMan](https://boards.straightdope.com/u/TroutMan)\ **Post date:** [March 22, 2013, 8:52pm UTC](https://boards.straightdope.com/t/non-toxic-reflective-liquids/653674/4 "2013-03-22T20:52:45Z")
Here are details on the ethylene glycol suspensions. It’s probably beyond the means of the typical kitchen chemist, but not impossible. [http://pubs.acs.org/doi/abs/10.1021/cm801075u](http://pubs.acs.org/doi/abs/10.1021/cm801075u)