The Bone "Lick Test"

[RyanDye]

Most people who have spent a fair amount of learning about paleontology know about "the lick test", but I still can't find a real explanation to why your finger sticks to material that's porous when its wet. The only thing I've found explaining it, is basically just a rephrasing of the test itself, for example "Because it's porous" I've also heard that the saliva gets sucked from your finger into the porous material, but why does your finger stick from that?  

[Miocene_Mason]

Look up capillary action, it’s a property of water. It’s also how vascular plants that have no muscles can transfer water.

[RyanDye]

4 minutes ago, WhodamanHD said:

Look up capillary action, it’s a property of water. It’s also how vascular plants that have no muscles can transfer water.

Also, are fossils still porous if they go through permineralization? 

[ynot]

4 minutes ago, RyanDye said:

Also, are fossils still porous if they go through permineralization? 

This depends on the state of mineralization.

I am not a fan of the "lick test" as there are many rocks that are porous and will "stick".

As mentioned above, the capillary action will cause a suction that makes porous rock stick.

[RyanDye]

5 minutes ago, ynot said:

This depends on the state of mineralization.

I am not a fan of the "lick test" as there are many rocks that are porous and will "stick".

As mentioned above, the capillary action will cause a suction that makes porous rock stick.

Could you also explain how the burn test works, as well as why when you tap a fossil on certain materials it makes a unique sound?

[Miocene_Mason]

3 minutes ago, RyanDye said:

Could you also explain how the burn test works, as well as why when you tap a fossil on certain materials it makes a unique sound?

Burn test checks for collagen, and the sound is looking for a rock rather than a bone sound. None of these tests are definitive. They are more like field tests.

 

21 minutes ago, RyanDye said:

Also, are fossils still porous if they go through permineralization? 

Another source of error which is that some bone will be filled in with minerals. You know like that agatized bone you see for sale. It’s best you learn what bone looks like. 

[RyanDye]

1 minute ago, WhodamanHD said:

Burn test checks for collagen, and the sound is looking for a rock rather than a bone sound. None of these tests are definitive. They are more like field tests.

 

Another source of error which is that some bone will be filled in with minerals. You know like that agatized bone you see for sale. It’s best you learn what bone looks like. 

Yeah, I know the tests aren't 100% accurate, I'm doing a demonstration speech in, go figure, my speech class, and the only thing I could think of for demonstrating paleontology were these tests.

[doushantuo]

Bone diagenesis an/or alteration depends on several factors,BTW:original porosity(structure of the bone,eg. trabecular or not),kind of burial,(subaerial,subaqeous(underwater),mixtures of both are not unthinkable ),climate,biotic attack(insects,bacteria ,fungi,rodents,hyena's etc ),hydrology/hydrochemistry.

There's some evidence of Ostwald ripening in bones,which would change the crystallinity.

The hydrolysis of collagen might liberat protons,thus changing the local pH

Bone minerals are insoluble above a pH value of 8,and in most environments all organics re gone after 15 years

[Miocene_Mason]

2 minutes ago, RyanDye said:

Yeah, I know the tests aren't 100% accurate, I'm doing a demonstration speech in, go figure, my speech class, and the only thing I could think of for demonstrating paleontology were these tests.

You could go for evolution if your school allows it. Easy to see in say, evolution from Angustidens to chubutensis to Megalodon. Good luck on your speech!

[RyanDye]

Just now, WhodamanHD said:

You could go for evolution if your school allows it. Easy to see in say, evolution from Angustidens to chubutensis to Megalodon. Good luck on your speech!

I have to demonstrate something, which is why it was difficult for me to come up with something.

[RyanDye]

Just now, RyanDye said:

I have to demonstrate something, which is why it was difficult for me to come up with something.

Like something physical, doing something physically with something.

[RyanDye]

46 minutes ago, WhodamanHD said:

Look up capillary action, it’s a property of water. It’s also how vascular plants that have no muscles can transfer water.

I looked up capillary action and watched multiple videos, but I still don't understand why your finger sticks to the material.

[Miocene_Mason]

3 minutes ago, RyanDye said:

I looked up capillary action and watched multiple videos, but I still don't understand why your finger sticks to the material.

You lick your finger adding water to its surface. When you touch the bone, the small holes in the bone (that coincidentally probably held capillaries) suck up the moisture on your finger which creates a small vacuum. This causes it to stick to your finger. Think of it like this, you have a bit of water in a water bottle and you drink the water all at once while not taking your mouth off the water bottle. You took out the water from the bottle, so now there is nothing where there was air, so the pressure off air outside forces the bottle to stick to your mouth. Same principle, except the bone uses capillary action whereas you are sucking out the water in the bottle example.

[ynot]

7 minutes ago, RyanDye said:

I looked up capillary action and watched multiple videos, but I still don't understand why your finger sticks to the material.

It will stick do to the suction created by the movment of the water.

[Miocene_Mason]

Quick simplified drawing of what happens. Before and after, the arrow points to vacuum.

 

[RyanDye]

4 minutes ago, WhodamanHD said:

Quick simplified drawing of what happens. Before and after, the arrow points to vacuum.

So that space where the arrow is there's nothing in there?

[RyanDye]

I understand the movement of water, but why does the movement of water create that vacuum? 

[Miocene_Mason]

7 minutes ago, RyanDye said:

So that space where the arrow is there's nothing in there?

More or less. Probably better to say low pressure than vacuum. Simply put water moves away, nothing fills its place. Because there is regular pressure outside, suction is created.

[RyanDye]

3 minutes ago, WhodamanHD said:

More or less. Probably better to say low pressure than vacuum. Simply put water moves away, nothing fills its place. Because there is regular pressure outside, suction is created.

Oh! Okay so what's happening is the air inside the bones becomes a lower pressure (or lighter in weight) than the outside air so the outside air is pushing against your finger making it "stick" when you lift your finger, the only thing I don't really get is why that water moving makes lower pressured air, or less air in that space than normal.

[Miocene_Mason]

1 minute ago, RyanDye said:

Oh! Okay so what's happening is the air inside the bones becomes a lower pressure (or lighter in weight) than the outside air so the outside air is pushing against your finger making it "stick" when you lift your finger, the only thing I don't really get is why that water moving makes lower pressured air, or less air in that space than normal.

Air does not weigh less, there is simply less of it. I think I understand your question now, and there is a few answers to it. Two things must be known here: There is not only one pore, and they all have different shapes and sizes and your finder is not stiff, the skin is pliable. 

 

For pores that have an open end, the water becomes a stopper. It pushes air already in it up and doesn’t let any down.

 

Ones that are closed have air pushed out by your finger (albeit very little) and the water forms a seal around the edges. Most of these also probably have microscoping pores that allow air to escape, which is then plugged up by water.

 

both of these have very little suction but there are many many pores so the effect is magnified.

 

I think. I’m no physics teacher.

[RyanDye]

7 minutes ago, WhodamanHD said:

Air does not weigh less, there is simply less of it. I think I understand your question now, and there is a few answers to it. Two things must be known here: There is not only one pore, and they all have different shapes and sizes and your finder is not stiff, the skin is pliable. 

 

For pores that have an open end, the water becomes a stopper. It pushes air already in it up and doesn’t let any down.

 

Ones that are closed have air pushed out by your finger (albeit very little) and the water forms a seal around the edges. Most of these also probably have microscoping pores that allow air to escape, which is then plugged up by water.

 

both of these have very little suction but there are many many pores so the effect is magnified.

 

I think. I’m no physics teacher.

I think a drawing would help me understand a little better, of course if your busy I can manage with that answer, thank you for sticking around so long to get this through my thick skull, I appreciate it! 

Edited September 9, 2018 by RyanDye
grammar

[doushantuo]

the consolation:

 

 

[RyanDye]

3 minutes ago, doushantuo said:

the consolation:

 

 

Well, if I had another idea for a demonstration speech about paleontology I wouldn't be inclined to try to explain this phenomenon, but as of now I don't have any idea what else I could do to demonstrate something physically relating to paleontology.  

[Miocene_Mason]

9 minutes ago, doushantuo said:

the consolation:

 

 

Ha, well at least it’s honest.

[RyanDye]

Maybe I should think of something else to demonstrate, but I just can't think of anything with bones or paleontology or anything of the sort that I could physically  demonstrate, any ideas?