I stumbled across the question Transparent resin to fill small acrylic plastic container?

At first glance the question seemed to be off-topic as asking for a product recommendation, so I started writing a comment linking to our help topic What topics can I ask about here?. While doing so, I felt more and more like nitpicking, because this question falls sqarely into a grey area between on-topic and off-topic...

The main section of the question is:

Some concerns, in rough order of importance:

1) Shrinkage. I want the resin to entirely fill the container once it has cured, with no gaps. If it shrinks and pulls away from the edges this would be bad.

2) Crazing or other chemical reactions with acrylic. I have heard that polyester resin (or maybe just the hardening catalyst?) reacts with acrylic plastic to cause crazing (tiny cracks) on the acrylic surface. This would be bad in my application. I am not sure if epoxy or other resins have this problem.

3) Ultraviolet transparency. Ideally I would like the resin to be completely transparent to ultraviolet, although some translucency (browning?) may be OK. (The glow-in-the-dark powder needs to charge.)

4) Transparency. I would like it to be as clear as practical. It is going to become somewhat translucent when I add the glow-in-the dark powder, so I would prefer to at least start fairly clear.

I would appreciate suggestions as to a resin or process that could satisfy these criteria.

Our help page states that questions about "Material selection and usage" and "Attributes of different media and how they interact" are on-topic, while "Product and service recommendations" are off-topic.

The OP didn't explicitely ask for a product or brand recommendation, but any answer could easily fall into into that category, depending on the person writing the answer.

I can see several more questions falling onto that grey-area searching for "kind material", like

My question is:

When is a question asking for product recommendations and therefore off-topic? What exactly is the difference between "material selection" and "product recommendation"? And do we need to clarify the difference in our help page?


The distinction is about asking about a type of product versus asking for a specific product.

A really simple example:

"What's the best type of brush to use for [this]?"


"Who makes the best fan brush for [this]?"

The problem can sometimes be distilling the full question down into its most basic form, and determining whether or not the OP was really looking for a specific brand/company/line/etc., or if they were just trying to determine if a product with their requirements even exists.

An incident that came up very recently was this question: Erasable blue pencils for sketching?

Which started some discussion and debate about whether or not it was a product recommendation question or not. But after reading through all the comments from the OP, it became clear to me that they were not asking for a specific brand, they were simply unaware that the category of "erasable colored pencils" even existed. And even if that category did not, the question could still be answerable in other ways. (Fictional examples: Use pencils with oil-based instead of wax-based binders. Watercolor pencils work well for this.)

So, I sided with keeping the question open (as always, I'm willing to listen to objections to that decision!).

Additionally, we also have a guideline that it's okay to cite specific products in the course of an answer, with the caveat that the answer isn't solely about recommending that one product. I intentionally tried to do this in my answer to the Erasable blue pencils question as a way to illustrate my point, but I know there are several answers here by others that do the same. Answers in the tag come to mind.

The help page might benefit from an update, but at this time I haven't felt that we've received product recommendation questions that make it seem like the help page is unclear. Most of the time when someone asks a product recommendation question, it feels very obvious that they simply didn't see that off-topic list at all. People that have read the off-topic list tend to make an attempt to frame their question more generically, and if they're not successful the community steps in and helps. I just don't know if there's concise enough verbiage to use when citing off-topic reasons for the gray area questions, especially since they tend to be unique in a way that suggests a meta question with the tag might be the best way to escalate.

Now, for me, I'm willing to be a little more lenient on answers that go into detail about specific brands, due to the nature of our stack. The "output" of users is semi-permanent. Artworks and crafts are long-term products that may need to survive in specific conditions for decades or longer. It therefore becomes important to use products that can be trusted to last, especially when a "test" is not feasible. (How do you personally test if the marker you chose is lightfast and holds it color 10 years from now?) Or, since many materials are essentially a chemical of some sort, it's important to use a product that clearly performs to spec or that lists its attributes. If Product Type 1 is generally heat-resistant, but only Brand A is rated for 200 degrees and other brands like B and C are only rated for 180 degrees, and you need 190, then the generic "type" might not be good enough.

This is unlike most of the other stacks, especially those that deal with technology or software. There's no 1-5 year churn of obsolescence, or constant new versions, or options to redo it in a year when the latest thing is released. Many arts & crafts supply manufacturers stick to a "always make it the same way" model specifically because of the longevity required of the products and the assurance that artists and craftspeople need that what they use today will be good in 20 years and if they buy it again 20 years from now it'll be the same thing.

Please note, though, that it's not leniency towards advertising or spam. What I'm okay with is expert artisans filtering their experiences, not shilling. It's also not a "rule", it's just the approach I'd start with to help interpret the community-driven rules if any debates started or flags were raised.


Web Head's answer does a good job of describing how to assess a question. I'll focus on the aspect of your question that refers to the answers on those questions.

You need to distinguish between the question and its answers. At best, a collection of only low quality answers suggests that the question might benefit from refinement and clarification. But you can't judge whether a question is on-topic by the answers.

The answers are basically irrelevant to whether the question is on topic, and they need to stand on their own merits. It's generally OK to recommend a specific product in an answer as long as it is actually a solution to the question and isn't spam. And when an answer does recommend a product, it should explain why that product is a good solution, and how to use the product to solve the problem in the question.

That's actually a simple way to differentiate whether the question is asking for a product recommendation. If the question is about a problem or requirement that needs solving, an answer should need to explain how to accomplish what was asked, or the nature of the required material. That can include a specific product recommendation. But if merely mentioning a specific product name is a complete answer to what was asked, that's a good indication that the question doesn't meet the standards.

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