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Below is the anatomy of a sandal:

enter image description here

The midsole is found in shoes, too, and I think that they serve the same purpose.

Question: What are the properties that should exist in a midsole for daily casual wearer?


What I have done so far:

I think the perfect daily casual midsole must have these properties:

  1. Should be flexible and maintain its flexibility despite water, salt, sun (UV).
  2. Should protect the feet from sharp objects, such as small rock pieces.
  3. Should be lightweight.

The best choices for mid/out-soles that I found so far seem to be:

  • EVA foam.
  • Synthetic rubber (used in tires). This is perhaps more suitable for outsoles (part facing the ground).

Looking forward to hear your properties.

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    I made heels with cast urethane on regular shoes ( cast onto the shoes) . It was more wear resistant than any other sole material and had excellent properties. I do not know the particular type of urethane . It was used to glue plastic foam together. Commented May 26, 2022 at 20:58
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    I'm wondering if there is a more direct and useful way to ask the question. Phrased like this, it isn't clear how one could translate any answers into something actionable in an on-topic way. Wouldn't it make sense to start with the purpose for each component, which would dictate its characteristics (I'm not sure the characteristics listed in the question are even the important ones for the midsole)? If you're trying to determine the best materials to use for the purpose, why not just ask about that? (cont'd)
    – fixer1234
    Commented May 26, 2022 at 23:25
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    Also, if the properties are what's important, it would be better to ask for quantified information (e.g., how flexible? compared to what? what materials would or would not be in a useful range? what materials are typically used?). There's probably a better way to ask for whatever you really want to know, and we can explore how to improve the question if you can elaborate on the information you need and how you want to use it.
    – fixer1234
    Commented May 26, 2022 at 23:25
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    How thick and stiff it needs to be depends a lot on what the footwear is for. Many sandals don't have a midsole, just two layers (or even one). Many smart shoes have just a thin hard sole and an insole. Sports shoes might have a double midsole or structure in the top of the sole. But cycling shoes are an extreme example with a thin stiff sole and midsole, while hiking boots can have chunky soles and midsoles stiff for only part of the length
    – Chris H
    Commented May 27, 2022 at 4:54
  • @ChrisH, your comment seems like the best way to answer this. Would you consider turning it into an answer?
    – fixer1234
    Commented Feb 7, 2023 at 1:22

1 Answer 1

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How thick and stiff it needs to be depends a lot on what the footwear is for:

  • Many sandals don't have a midsole, just two layers (or even one on cheap pairs).
  • Many smart shoes have just a thin hard sole and an insole.
  • Sports shoes might have a double midsole or structure in the top of the sole.
  • Cycling shoes are an extreme example with a thin stiff sole and midsole.
  • Hiking boots can have chunky soles and midsoles stiff for only part of the length.

So you need to decide what it's for. For many of these, as you say, EVA foam is used, but that's only half the story. There are different densities of EVA, and you don't even have to pick just one. EVA bonds well with urethane glues, including to any rubber you might use for the outsole, making it a good choice for a glued construction.

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