A question has arisen if shopping advice posts is off-topic and should be kept closed.


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Refractive index liquids: Why hard to buy?

Where can I get fluidics components?

I realise that this is not a question on physics, but how does one otherwise ask the fellow physicists for this kind of information? Experimental physics is to a large extent about choosing the right makers. Besides, the question 12466 is not just about where to buy these liquids, but mainly about why they are so rare on the market. I have never worked with them, so do not know, and was asking for help. People experience in refractometry / microscopy might have been able to answer question 12466.


I think questions about specialist equipment and materials is on topic. (Though I am not enough of a specialist to judge whether refractive index fluids are that special.)

While I am not an experimentalist myself, I do have a few in my family and close friends. And for a lot of the truly specialist objects the number of suppliers in the entire world can be counted on one's fingers. In this case if your familiar supplier takes a (possibly permanent) vacation, it can become difficult to find replacements. Further more, since these suppliers cater to special interest, there's relatively little point for them to make large advertising efforts (in trade magazines, on the internet, etc), since their potential customer pool is so small. All these combined means that the existence of these suppliers often pass by word of mouth. In this case I would say none of the usual objections to "shopping advice" questions would apply, and in fact a Community-Wiki list for this may be a great use of the site and a great service to the community.


Shopping questions are generally disallowed...


... however, all rules have exceptions!

I find that some rare shopping questions can be on topic if they:

  • are extremely specialized to your community
  • cover things that are difficult to find

Consider the utility and longevity of the question. Will this question be useful to someone in the US? the UK? South America? How about 5 years from now? This is where "typical" shopping questions fall apart, so if you can avoid those pitfalls, you're doing well.

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    $\begingroup$ For a lot of specialist equipment/materials, the number of suppliers in the whole world is rather limited, and most of those specialist companies stay in the business for a long time. So I think they should be exempted from the general prohibition of shopping questions. (I am not sure whether refractive index fluids is specialist enough, never needed any myself.) $\endgroup$ – Willie Wong Jul 20 '11 at 17:20
  • $\begingroup$ That seems to meet the criteria I outlined above. If it is highly specialized and rare some shopping questions can be OK. $\endgroup$ – Jeff Atwood Jul 20 '11 at 22:08

Since I closed the question in question, I figure I should say something: my reasoning is that this is a site for questions about physics. Asking where you can buy some product, regardless of what the product is, is not a question about physics. That's why I closed it. I wasn't thinking of the general prohibition on shopping recommendations on SE sites.

As I understand it, the proposal Experimental or Applied Physics on Area 51 is intended for exactly these sorts of questions.

If the community would like questions about obtaining lab equipment to on-topic here, I'm okay with that. It would represent a change from my existing moderation policy.

  • $\begingroup$ Maybe a compromise is to allow such questions until Experimental or Applied Physics enters public beta? We can always migrate the questions over there later. $\endgroup$ – Willie Wong Jul 21 '11 at 13:08
  • $\begingroup$ I think there should be understanding of the rules rather than simple following them. Prohibition of the shopping discussion most probably comes from the idea that any sort of advertisement should be avoided. As About says, "This is a... Q&A for active researchers, academics and students of physics." So I think it is most appropriate to ask here a tough question concerning searching speciality equipment or consumables. Where else? $\endgroup$ – texnic Jul 23 '11 at 9:46
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    $\begingroup$ Aside from this argument above, I just fully agree with Willie and Jeff. This question is of interest worldwide (because I couldn't find any competitors of this one company, and I'm actually exactly outside the US) and, unless the situation changes, this question will be relevant in 5 years, since Cargile is on the market since 1920s. I would like to ask once again to reopen the question. $\endgroup$ – texnic Jul 23 '11 at 9:46
  • $\begingroup$ @texnic: well of course you'll agree with them, it's your question ;-) Anyway: to judge what is on topic here, you should look at the FAQ, not at the popup banner. The FAQ lists four topics that are definitely appropriate here: (1) Explanations of observed physical phenomena, (2) Experimental designs and results, (3) Accepted and/or actively researched theories, (4) Mathematics and physics (and computational physics will probably be added). Your question doesn't fall under any of those areas, so it's not manifestly on topic. $\endgroup$ – David Z Jul 23 '11 at 17:48
  • $\begingroup$ My issue at this point is that none of the responses to this question have actually addressed the reason I consider the question off topic. Willie and Jeff have been saying that your question doesn't run up against the general ban on shopping questions, which I can agree with, but that's not why I closed it. I'd like to see some more input from others that specifically addresses the reason I gave, and more generally whether the kinds of questions that would fit on the Experimental or Applied Physics proposal should be considered on topic here. $\endgroup$ – David Z Jul 23 '11 at 17:57

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