Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

Do salt lamps really produce negative ions? Do you know about any scientific study that could support this assertion or disprove it?

share|cite|improve this question
Phrased as it is, i.e. essentially a reference request, I guess this would fit better on Skeptics.SE – F'x Mar 18 '12 at 11:28
@truthseeker: do you want a hard reference or a scientific explanation from anyone? – Manishearth Mar 18 '12 at 12:55
@F'x anyways, I'll mark it for migration. – Manishearth Mar 18 '12 at 12:56
I dislike this question because it implies that 'negative ions' are something special and exotic, and that salt crystals might also be special and exotic. It's just a hunk of salt and an incandescent lamp! – nibot Mar 18 '12 at 18:14
@nibot: 'negative ions' are special and exotic to almost everybody outside of science and engineering. – Alexander Mar 18 '12 at 19:53
up vote 4 down vote accepted

There is no study because there is no physical mechanism were a salt crystal sends negative ions into the air without any energy input. Just heating the inside up with an incandescent lamp warms the lamp a bit but this does not create any measurable amount of negative ions.

There are ion generators but these work on a completely different principle. Basically you need a very high electric field to ionize air molecules or dust particles. Here is a study that explains how the air quality is positively influenced by a air purifier that creates negative ions.

share|cite|improve this answer
Absence of proof vs. proof of absence… I agree with your answer for the physics, but there could be a study (and there probably is, somewhere) aimed at demonstrating that indeed, salt lamps heated with an incandescent lamp do not yield negative ions. – F'x Mar 18 '12 at 17:00
@F'x: I think it's quite unlikely. A scientific study is work- and time consuming and who would want to fund such an endeavour and it is hard to prove a negative anyway. – Alexander Mar 18 '12 at 17:12
Mechanism: "Some salt lamp manufacturers claim that the natural absorption of moisture and its subsequent release through the heating effect of the lamp, releases negative ions. Is this a fact?" – endolith Mar 19 '12 at 16:17
@endolith: If a salt crystal becomes wet there will be a solution of Cl- and Na+ ions in water at the surface. The evaporation of Cl- ions in a water droplet is possible, that the whole droplet is negatively charged still unlikely. Reductio ad absurdum: A pot of boiling salt water would create a gigantic amount of negative ions. – Alexander Mar 19 '12 at 16:57

This website addresses this issue. I have no idea how rigorous it is but it is interesting.

share|cite|improve this answer

protected by Qmechanic Feb 1 '13 at 13:33

Thank you for your interest in this question. Because it has attracted low-quality or spam answers that had to be removed, posting an answer now requires 10 reputation on this site (the association bonus does not count).

Would you like to answer one of these unanswered questions instead?

Not the answer you're looking for? Browse other questions tagged or ask your own question.