Sponges and Rate of Water Retention

I'd think that the cells of a wet sponge would already be partially expanded and would accept water more readily.

Have you performed any timed experiments?

If you take two sponges, saturate one sponge and wring it out, then compare its speed of saturation to dry sponge, I would expect the wet sponge to acquire water faster because the open cells are already expanded.

Whereas the dry sponge needs time to expand as Lyn pointed.

You could try an experiment with two identical sponges (one wet, one dry) and two identical glasses partly filled with water and see how fast each glass's levels drop.

I'd agree with the surface tension theory.

Most commercial sponges are made from plastic, which will not readily absorb water.

It also depends on the porosity of the sponge, which is kind of described here.

Water will move more quickly into something that is already damp...same happens in a heavy rain; it will quickly run off from dry soil, but will be more readily absorbed by soil that is already slightly damp.

"Most commercial sponges are made from plastic,"

I always avoid those plastic sponges and choose cellulose based ones, because the plastic ones don't absorb liquids worth a darn.

To the OP:

In addition to capillary action, water molecules are cohesive.

And, it is di-polar. Unlike some of our members who are bi-polar.

There are a couple reasons why wet sponges soak up more
water than dry sponges. The first one has to do with the sponge. It's
made with tons of tiny holes. When the sponge is dry and water
flows into it, a lot of the water escapes through these holes. As the
sponge gets more wet, it swells from all the water it is taking in, and
a lot of those holes get filled up, so not as much water can escape.
The second reason has to do with water itself. Water is very sticky
stuff, that's why you have to dry your hands after you wash them,
because there's still water sticking to them. Water molecules stick
especially well to other water molecules, because they're highly
attracted to one another. This means that if a sponge is already wet,
the water in the sponge will grab hold of the water being poured into
it, so the sponge absorbs more water.

Not "more" water; it will absorb water "faster".

Thanks for that, however i was relating it to the time duration not the volume. You are right it will not absorb more water over a 10 minute period of time, however in 10 seconds it will absorb more water. The question to me appeared to be why it absorbed faster, so i focused on the speed and not the volume.

Thanks again and i do really appreciate your great posts and obvious sense of humor

I don't know why, buy I was thinking about this as I was drifting off to sleep last night.

I was thinking about swabbing the decks way back in my Navy days, and somehow, it was just a known fact to pre-wet the mop and wring it out before starting to clean up a spill or a mess; a dry mop would just push things around, with very little wicking.

I was a proud member of the US Navy Mop brigade as well

The downside is i learned so well now my wife wants me to do all the mopping!

she keeps trying to use those cheezy cleaning pads, brand name withheld, that you push across the floor and replace every 2 minutes. someone obviously is making alot of money on that ridiculous invention. Nothing cleans like the old wet mop.

Thanks for bringing back the nightmare memories!

I was working on a job a couple of weeks ago, and the owner of the house pulled out a can of this.

I almost had a violent reaction.

"....When the sponge is dry and water

flows into it, a lot of the water escapes through these holes....."

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Really? When you put a dry sponge in standing liquid, the water flows in, but then some of it escapes!?! Where? Out the sides and top?

I want some of the sponges you use!

Fortunately for you it only takes 500 comments on CR4 to get Guru status!

I will not even try to explain the principle of porosity to you, You are the Guru you figure it out

Darn,

I thought that maybe there was a spark of intelligence there.

Guess not.

Just Lynoogling like the rest of you!! And i nearly never see a credit for things on here. but you still only need 500 posts to be a Guru and to get a GA you just have to have the most sarcastic comment or ridiculous photo as well.

Start your own forum. Then you can screen the members and only allow those in who are jerks, like you.

My, oh My, Take another Prozac, you need to re-read a couple of your posts it should only take 1 or 5, and start your own forum.

"I thought that maybe there was a spark of intelligence there.

Guess not. "

You are way better than I am. That being said I quite enjoy the conversations on here and hope in some way to help a couple of people out every now and then.

I certainly don't want to give the perception that I am a jerk. I have at times shared your frustration with ridiculous posts, however that makes it interesting. I also do feel that I have offered some good posts as well.

I do have to agree with doorman in his post.

http://cr4.globalspec.com/comment/951967

I have too great a life to spend it bickering back and forth with a few old codgers.

I would rather spend my time helping others in need, sharing wisdom that I may have accumulated, and enjoying life.

I do apologize for being hasty and not linking to the site in my earlier post and have gone back and added it.

I will defer to your great wisdom however and if you would like I can quickly unsubscribe or I can take to posting anonymously as others do ( I could really get under your skin then). I will leave that up to you!

Whatever you say is fine with me.

Hey Doorman, did you mean to write Plagiarism? When you can't come up with a good answer just crack on the other people, that will get you a GA for sure!

http://www.madsci.org/

Okay, so that is the source of your verbatim copy.... still, the question remains: do you seriously believe water is flowing into holes in a dry sponge and escaping to somewhere else? Where exactly?

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When you put a sponge into a pool of water, where is the magical place where the water entering the dry sponge 'escapes' to?

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What you have demonstrated is not an eye for a good explanation (but no appreciation of crediting the work of others); what has been demonstrated is blind belief in an explanation you don't seen to understand well enough to support, and the ability to credit your source once someone calls you out for failing to do so.

damp open sponge cells + capillary action + cohesion

I think some additional details need to be clarified. Two specific things stick out:

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1. Does 'dry sponge' mean a sponge as it comes new, pliable but no water that could be wrung out?....or does it mean a sponge that has been well used and then completely dried out, such that it is stiff and significantly smaller than the size it will be when wet again?

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2. The process by which the sponge is soaking up the water also matters. Are the sponges simply being placed in the standing water?... or is the sponge experiencing diminishing compressive forces as it is wiped through the standing water (by hand or handle)?

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If your observations relate to a sponge in active use, I think diminishing compression on the sponge plays a large role. This is especially true when considering a used, dried out sponge, since it is far less pliable.

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If your observations relate to a sponge just placed in standing water, there are other factors that come into play, such as buoyancy. The dry sponge floating completely on the surface will not have the same contact area as the wet sponge which displaces the water and rests on the surface below.

Actually, if you compress a WET sponge completely flat, then quickly drop it into a shallow bowl of water it will absorb water a great deal faster than a damp sponge or a dry sponge.

I agree with you concerning a completely dry sponge.

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I do have to ask, is there a difference between a wet sponge that has been compressed completely flat, and a damp sponge that has been compressed completely flat?

There just might be. It'd be worth experimenting a bit...

With the wet or damp sponge compressed and quickly released, you have several other forces being applied: the elastic forces of the sponge returning itself to its default size and shape, thereby creating a partial vacuum in the inside of the sponge, which allows atmospheric pressure to aid pushing water up into the sponge, as it does up a straw. In a somewhat wet sponge, the extra water might help to seal the pores and retain the vacuum better.

I would say if you compress a wet sponge completely flat you will get a damp sponge.

The delay in the dry sponge has to with wetting. As it reaches a balance between cohesive and adhesive forces of the molecules.

Dr. Harry-

Don't have the exact answer you want, but it may help to see the question in the relativity between the two sponges. Have you considered wetting a sponge, wringing it out, placing it in a small dish on a scale and weighting it for a tare weight? Weigh the dry sponge n a similar dish and this would be it's tare weight.

Place both sponges in a tray of water for a short but identical period of time, whatever you like. Remove each sponge and place each back in their respective dish. Weigh each sponge/tray for the gross weight of each. Subtract tare from gross and you have net weight of each sponge.

This procedure would give you an idea of how much the difference in net weight, expressed in %, between each sponge is. The net weights per time could also be derived and give you a figure for the rate of absorption. This way you can see if the amount and rate is very large, very small, or insignificant. Perhaps small differences means don't waste you time further or large differences should be investigated further.

Good Luck, Old Salt

I

Is this likely due to the surface tension of the water in the http://www.mmokiss.com