20 votes

Why are drink coasters flat?

A drink coaster goes under a glass or cup, and is intended to catch any condensation or spillage from the glass, to protect the tabletop underneath.

But most coasters are flat.* Any liquid that gathers on them can roll off the edges onto the table. Some coasters are made of a water-absorbing material, like cardboard or cork, but some are made of materials that repel water, like metal or ceramic or plastic.

I ask this because I recently discovered a small coaster-like tray with an upraised lip around the edge. Strictly speaking, it's not a coaster, but it's exactly the right size to be used as a coaster - and, with the upraised lip around the edge, it actually prevents liquid from escaping onto the table.

So why are coasters flat?

(I bought some of the lipped not-coasters to use as coasters. This design makes sense to me. And they happen to look nice as well.)

* It was only while researching coasters online prior to making this post that I discovered that some coasters have lips. Every coaster I've seen in real life is flat.

23 comments

  1. [3]
    acdw
    Link
    I bet cost has a lot to do with it. Especially cheap coasters, which are common tourist trinkets, it's gotta be way cheaper to print a sheet of plastic and cut it into circles or squares than to...

    I bet cost has a lot to do with it. Especially cheap coasters, which are common tourist trinkets, it's gotta be way cheaper to print a sheet of plastic and cut it into circles or squares than to individually mold a lip onto each one.

    I've definitely seen nice coasters made of cork with a lip though.

    10 votes
    1. [2]
      pseudolobster
      Link Parent
      I've seen coasters with a lip and a recessed cork section too. Cost is one thing, but another is stackability. I'd guess the majority of coaster buyers these days don't want their coaster...

      I've seen coasters with a lip and a recessed cork section too. Cost is one thing, but another is stackability. I'd guess the majority of coaster buyers these days don't want their coaster collection taking up a ton of space.

      Every inset coaster with a recessed area I've ever seen has been a part of a "coaster set" that comes with a stand / little cabinet to contain the coasters. They take up at least 3x the vertical height of standard ones, and I think that's gotta be a big reason why I've only ever seen them in the houses of really old people who only own six coasters total, and some tiny wooden cabinet with brass knobs on its doors to hold them. Old people used to make a big deal about these, and try and show them off to their guests. "Oh, my! What nice coasters you have!" they'd say.

      As for cost, I'm thinking the cost of making tiny hand-fabricated wooden cabinets with dovetail joints and lathe-turned wooden coasters with hand-glued cork inserts is no longer worth it since the current generation will never want to show off their coasters to guests. Now it's assumed there's some kind of wood 3d printer that can pump these things out for a hundredth of a cent per piece, and if anyone ever found out you spent more than a dollar per coaster they'd look at you like you're crazy.

      11 votes
      1. acdw
        Link Parent
        I have some coasters made by my cousins husband, and though they are just limb sections I love them and love displaying them. Maybe we should have little cabinets again! I am there for it.

        I have some coasters made by my cousins husband, and though they are just limb sections I love them and love displaying them. Maybe we should have little cabinets again! I am there for it.

        2 votes
  2. [8]
    mrbig
    Link
    Maybe the amount of condensed liquid is not enough to require a non-flat surface.

    Maybe the amount of condensed liquid is not enough to require a non-flat surface.

    6 votes
    1. NaraVara
      Link Parent
      Basically this. A lip is a “nice to have” rather than a “must have.” The issue isn’t that any amount of water is bad, it’s that soaking a wooden table in water for an extended length of time is...

      Basically this. A lip is a “nice to have” rather than a “must have.” The issue isn’t that any amount of water is bad, it’s that soaking a wooden table in water for an extended length of time is the problem. So a little moisture running off isn’t a big deal.

      Also, with smooth surfaces the coaster is as much about keeping condensation from making an annoying seal that adheres your cup in place as much as it is protecting the finish on the table.

      7 votes
    2. [6]
      Algernon_Asimov
      Link Parent
      It is on the drink I'm having right now. :) If I had a flat coaster right now, there's enough water under my glass that it would be dripping off the edge.

      It is on the drink I'm having right now. :)

      If I had a flat coaster right now, there's enough water under my glass that it would be dripping off the edge.

      1 vote
      1. patience_limited
        (edited )
        Link Parent
        I think you may have answered your own question, there. Condensation happens on refrigerated surfaces in humid air. The original coasters wouldn't have been protecting surfaces from drinks as cold...

        I think you may have answered your own question, there. Condensation happens on refrigerated surfaces in humid air.

        The original coasters wouldn't have been protecting surfaces from drinks as cold as they are with modern refrigeration, more just dribbles. I thought coasters first became popular as part of beerhall advertising - cheap printed cardboard that alluded to how cold and frosty the beer glasses were served.

        Otherwise, spillable liquids got served in cups with saucers, for the fancy folk with fragile furniture. (It might also explain the bloody stupid stemmed cocktail glass - keeping the wet part away from the table?)

        Even now, refrigeration + air conditioning means not much surface condensation. So your basic coaster doesn't need to contain a great volume of liquid. Unless you're outdoors in tropical summer!

        Also, I've seen serviceable silicone coasters which have a Lego-like nubbed surface so you can set your drink down flat, but the depth of the coaster will still hold a volume of condensate. Not sure how easy it is to pick up the coaster without dumping it, but it seems a reasonable design, and they're not expensive.

        4 votes
      2. [4]
        mrbig
        Link Parent
        What are you drinking, buddy? You know, for science!

        What are you drinking, buddy? You know, for science!

        1. [3]
          Algernon_Asimov
          (edited )
          Link Parent
          Here 'tis. For science!

          Here 'tis. For science!

          1 vote
          1. [2]
            mrbig
            Link Parent
            Cool. We don't have vanilla variations here, but we have Guaraná Antarctica, which is pretty great.

            Cool. We don't have vanilla variations here, but we have Guaraná Antarctica, which is pretty great.

            1. Akir
              Link Parent
              I'm not likely to go to Brazil any time soon, but if I ever do, I will make it a point to try that one out.

              I'm not likely to go to Brazil any time soon, but if I ever do, I will make it a point to try that one out.

  3. [5]
    MimicSquid
    Link
    I'm not sure about this either. Especially because flat, smooth coasters can also cling to the bottom of the glass when you pick it up, leaving the wet coaster to drop into your lap when it falls off.

    I'm not sure about this either. Especially because flat, smooth coasters can also cling to the bottom of the glass when you pick it up, leaving the wet coaster to drop into your lap when it falls off.

    2 votes
    1. [2]
      Algernon_Asimov
      Link Parent
      A lip wouldn't necessarily prevent that: the centre of the coaster would still be flat and smooth enough to cling to the bottom of the glass. Fixing this problem would require the coaster to have...

      A lip wouldn't necessarily prevent that: the centre of the coaster would still be flat and smooth enough to cling to the bottom of the glass. Fixing this problem would require the coaster to have an uneven surface, not a lip.

      2 votes
      1. MimicSquid
        Link Parent
        True. This is why my ideal is a wooden, lipped coaster with a cork bottom. You get the absorption of the cork, and a more sturdy outer shell.

        True. This is why my ideal is a wooden, lipped coaster with a cork bottom. You get the absorption of the cork, and a more sturdy outer shell.

        1 vote
    2. [2]
      kfwyre
      Link Parent
      I've gotten plenty of confused stares (and subsequent ribbing) from friends for this, but if you salt a coaster or napkin, it won't cling to the bottom of a wet glass. I do it all the time at...

      I've gotten plenty of confused stares (and subsequent ribbing) from friends for this, but if you salt a coaster or napkin, it won't cling to the bottom of a wet glass. I do it all the time at restaurants.

      1 vote
  4. [2]
    Comment deleted by author
    Link
    1. Algernon_Asimov
      Link Parent
      I'm not talking about a high lip. It only needs to be a few millimetres high to stop the water running off the edge. Yes, a moat is also a good option, but I haven't seen coasters like that.

      I'm not talking about a high lip. It only needs to be a few millimetres high to stop the water running off the edge.

      Yes, a moat is also a good option, but I haven't seen coasters like that.

      2 votes
  5. asoftbird
    Link
    Seems like it'd add a whole new dimension to production costs; insteas of just cutting circles from a sheet you're now also moulding / glueing something on the things. That might add a lot of...

    Seems like it'd add a whole new dimension to production costs; insteas of just cutting circles from a sheet you're now also moulding / glueing something on the things. That might add a lot of costs to the product.

    1 vote
  6. [4]
    DanBC
    Link
    Beer mats are flat and absorbent, so they'd help, but are somewhat wasteful. I've seen some double sided coasters - one side is flat, the other has a pattern of raised dots. These raise the glass...

    Beer mats are flat and absorbent, so they'd help, but are somewhat wasteful.

    I've seen some double sided coasters - one side is flat, the other has a pattern of raised dots. These raise the glass up and provide a space for drips.

    I always thought that the coaster was to protect the table against heat, not water, which is why they're made from insulating material like cork. And that the saucer is used to protect against drips (so why don't glasses come with saucers?)

    But I've never checked, and so maybe this is bollocks.

    1 vote
    1. [2]
      mat
      Link Parent
      I was also of the opinion that the point of a coaster was to protect the surface from heat. If you put a hot cup of tea or coffee down on a French polished surface, it can leave a mark. Modern...

      I was also of the opinion that the point of a coaster was to protect the surface from heat. If you put a hot cup of tea or coffee down on a French polished surface, it can leave a mark. Modern wood finishes don't mind heat (or water, for that matter) so coasters are largely redundant as functional items.

      So I would say that coasters are flat because they're a hangover from a previous time when tables needed protecting, and they never really existed to solve the drip problem in the first place.

      4 votes
      1. vivaria
        Link Parent
        Is there something to be said for the psychological comfort that comes with a coaster? When I put a drink down on a table bare, I get a bit of mild anxiety that something's off. I don't want to...

        Is there something to be said for the psychological comfort that comes with a coaster?

        When I put a drink down on a table bare, I get a bit of mild anxiety that something's off. I don't want to leave a ring of condensation on the table! It feels messy, and I'd just have to wipe it up anyway. Having a coaster feels more proper and neat and polite.

        Even if there's no risk of damaging tables, it still feels better to me to have one.

        4 votes
    2. Algernon_Asimov
      Link Parent
      Exactly. That's my question, but phrased differently. :)

      And that the saucer is used to protect against drips (so why don't glasses come with saucers?)

      Exactly. That's my question, but phrased differently. :)

      2 votes
  7. vorotato
    Link
    Often coasters are a slightly absorbent material, enough to not have the water puddle, but not enough to reach the other side of the coaster.

    Often coasters are a slightly absorbent material, enough to not have the water puddle, but not enough to reach the other side of the coaster.

    1 vote