Used this example before, but if you tried putting your hydrometer into a trial jar of porridge im sure you'd get a pretty high reading
even though the oats aren't dissolved in the milk/water (same principle).
All grain gravity is it 'real'
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delboy
Not sure strictly the case, i dont think the particles need to be dissolved/hydrated they just need to be in suspension. Hydrometers are routinely used to measure suspended particles ie the amount of clay in silt etc.
Used this example before, but if you tried putting your hydrometer into a trial jar of porridge im sure you'd get a pretty high reading even though the oats aren't dissolved in the milk/water (same principle).
Used this example before, but if you tried putting your hydrometer into a trial jar of porridge im sure you'd get a pretty high reading
even though the oats aren't dissolved in the milk/water (same principle).-
SteveD
I don't think your example is representative. If there are solids in the liquid where there is a comparatively large ammount of liquid - eg trub in wort, I can't see that affecting the SG. The porage example would be akin to straining off the wort and just having the wet trub. I expect that would confuse the reading too! If on teh other hand you had a few oats floating around in milk I expect you'd get the same result as milk alone - that's not porage. Not how I like it, anyway. 
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delboy
ok bad example but the principle remains the same. If you think about the wort at the molecular level rather than at the can i see it level, it would be chock full of proteins (much like the thick bowl of porridge). Lets face it we can't see the sugars but we still believe the wort is full of them
From what im seeing the large clumps of trub that you can see don't seem to make much difference to the gravity (because they aren't truly in suspension i guess). These settle out rather quicky leaving what would apper to be clear wort (wort measured an hour after collecting still had high gravity).
Im guessing its the proteins that you can't see ie the ones truly in suspension that are responsible for the higher gravity. These take much longer to fall out of suspension overnight for example (which is when i see the significant fall).
From what im seeing the large clumps of trub that you can see don't seem to make much difference to the gravity (because they aren't truly in suspension i guess). These settle out rather quicky leaving what would apper to be clear wort (wort measured an hour after collecting still had high gravity).
Im guessing its the proteins that you can't see ie the ones truly in suspension that are responsible for the higher gravity. These take much longer to fall out of suspension overnight for example (which is when i see the significant fall).
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UserDeleted
Its quite simple really. Take your hops at the end of the boil and squeeze them out into a jug. Pour that into your hydrometer sample jar and take the gravity. Remove the hydrometer and let it settle. Add the hydrometer again and it will get stuck in the break material.
In short If it is in the hydrometer jar it will affect the reading on the hydrometer, which simply shows the relative difference in weight between your sample and a sample of water.
Hydrometers work on the principle that a molecule has the ability to turn polarised light in a given direction by a given amount. for each molecule this is known, and instruments can be calibrated to this particular level. Of course there is some interaction between molecules (hence the fuzzy line
), but in general they can be pretty specific. Although I do know one homebrewer who uses a refractometer calibrated to read urine and a lookup table to convert back to maltose / brix Oh and its a $300 refractometer!!
Lets not even consider a mixture of laevorotatory and dextro rotatory molecules
In short If it is in the hydrometer jar it will affect the reading on the hydrometer, which simply shows the relative difference in weight between your sample and a sample of water.
Hydrometers work on the principle that a molecule has the ability to turn polarised light in a given direction by a given amount. for each molecule this is known, and instruments can be calibrated to this particular level. Of course there is some interaction between molecules (hence the fuzzy line
), but in general they can be pretty specific. Although I do know one homebrewer who uses a refractometer calibrated to read urine and a lookup table to convert back to maltose / brix Oh and its a $300 refractometer!!Lets not even consider a mixture of laevorotatory and dextro rotatory molecules
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SteveD
I believe the second bold red word is what you meant?UserDeleted wrote:
Hydrometers work on the principle that a molecule has the ability to turn polarised light in a given direction by a given amount. for each molecule this is known, and instruments can be calibrated to this particular level. Of course there is some interaction between molecules (hence the fuzzy line
Lets not even consider a mixture of laevorotatory and dextro rotatory molecules
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mr.c
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SteveD
It seems logical to me, and there must be something writen about this, but it's the weight of the liquid that the hydrometers measure. Assuming it's not physically resting on break material, or otherwise being obstructed, the weight of solid floating about in the liquid being measured is irrelevant. The only time it might matter is if the solid had precipitated out of the solution being measured.
Example :- Take one large test jar. Fill it with sugar solution. Take the OG, say 100. Then drop a quantity of inert sand into it. Take OG again. I can't see how it can be anything other than 100 again.
If on the other hand if the solid precipitated out of the solution eg trub or sugar crystallising out, the reading would go down, right? But would it?? If the volume stays constant, you'd say yes. But I don't think it does. As the solid precipitates out, does the volume of liquid not reduce as a result? Reduced volume increases the concentration of the remaining liquid, possibly negating the effect of the precipitation and resulting in a reading that does not perceptibly change.
Note, This is all just my opinion. I haven't read anything about this anywhere.
Example :- Take one large test jar. Fill it with sugar solution. Take the OG, say 100. Then drop a quantity of inert sand into it. Take OG again. I can't see how it can be anything other than 100 again.
If on the other hand if the solid precipitated out of the solution eg trub or sugar crystallising out, the reading would go down, right? But would it?? If the volume stays constant, you'd say yes. But I don't think it does. As the solid precipitates out, does the volume of liquid not reduce as a result? Reduced volume increases the concentration of the remaining liquid, possibly negating the effect of the precipitation and resulting in a reading that does not perceptibly change.
Note, This is all just my opinion. I haven't read anything about this anywhere.
Last edited by SteveD on Mon Mar 26, 2007 8:43 pm, edited 1 time in total.
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SteveD
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mr.c
"It's better to be a fool for 5 minutes of your life by asking a question than to be a fool for the rest of your life by not knowing the answer"SteveD wrote:You just did.mr.c wrote:Just read the posts,so am i going about it in the wrong way
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PieOPah
When I next brew I am going to use a sinle sample and take readings (both gravity and brix) over a period of time. Hopefully this will enable us to work out whether the readings we take are accurate straight away or not!
unless of course somebody brews before me and decides to work this out and post the results themselves
unless of course somebody brews before me and decides to work this out and post the results themselves
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delboy
UserDeleted wrote:Its quite simple really. Take your hops at the end of the boil and squeeze them out into a jug. Pour that into your hydrometer sample jar and take the gravity. Remove the hydrometer and let it settle. Add the hydrometer again and it will get stuck in the break material.
In short If it is in the hydrometer jar it will affect the reading on the hydrometer, which simply shows the relative difference in weight between your sample and a sample of water.
Hydrometers work on the principle that a molecule has the ability to turn polarised light in a given direction by a given amount. for each molecule this is known, and instruments can be calibrated to this particular level. Of course there is some interaction between molecules (hence the fuzzy line
Lets not even consider a mixture of laevorotatory and dextro rotatory molecules
Hi UD sorry im a bit thick but i didn't really follow your wee example above what where you trying to say? Our my orginal gravity readings correct (which is what i want to hear) or is it the overnight sample?
Im simple terms when i see a drop of close on 20 gravity points (from 1060) when leaving the sample overnight to what would you attribute that to??
I can't remember the refractometer being calibrated in the way you describe i used to set up Caesium Chloride and sucrose gradients (we used to zero it for a solution ie a known amount of sucrose or a known amount of CsCl but the machine itself has absolutely no discriminatory powers ie it couldn't have told the difference between the two).
To be fair it was like somethingh out of the arc and maybe the world of refractometery has moved on (although its basically just a prism whatever way you cut it) so i'll bow to your superior knowledge.
Yeah that would be a did of a doosy what with all natural sugars in the D-form and all natural proteins in the L-form, seems like they would be competing with each other for the light bending.
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delboy
Go out to your garden get a handful of soil put it in some water and shakeSteveD wrote:It seems logical to me, and there must be something writen about this, but it's the weight of the liquid that the hydrometers measure. Assuming it's not physically resting on break material, or otherwise being obstructed, the weight of solid floating about in the liquid being measured is irrelevant. The only time it might matter is if the solid had precipitated out of the solution being measured.
Example :- Take one large test jar. Fill it with sugar solution. Take the OG, say 100. Then drop a quantity of inert sand into it. Take OG again. I can't see how it can be anything other than 100 again.
If on the other hand if the solid precipitated out of the solution eg trub or sugar crystallising out, the reading would go down, right? But would it?? If the volume stays constant, you'd say yes. But I don't think it does. As the solid precipitates out, does the volume of liquid not reduce as a result? Reduced volume increases the concentration of the remaining liquid, possibly negating the effect of the precipitation and resulting in a reading that does not perceptibly change.
Note, This is all just my opinion. I haven't read anything about this anywhere.
the living daylights out of it. Put your hydrometer in and watch as the
sediment falls so will the hydrometer reading. Yet the hydrometer will not
physically be 'held up' by soil matter in the sense that we would
understand it.
Sand would be a bad example it will sink in seconds and won't go into suspension whereas soil will be composed of all sizes of particle some that will fall out immediately and some that will remain in suspension for quite some time.
To my mind the hydrometer is not measuring the weight of the liquid but the measuring the ability of a liquid to resist the force of a hydrometer (its weight) required to sink into the liquid (my own definition not from wiki or any books so feel free to pull it to bits).
Thats why when there is plenty of sugars (or proteins) in solution the vicosity/density/gravity call it what you will, of the liquid increases. This causes an increase in viscosity of the liquid ie becomes more solid like and therefore the hydrometer does not sink into the liquid as much. This is why when the liquid is above 20C the hydrometer sinks more.
At higher temps the viscosity or ability of the liquid to resist force is reduced because the molecules are more spaced out ie expanded (not that it suddenly weighs less).
Conversely when its colder the readings go up because the molecules are closer (and better able to resiist exerted force) ie contracts becoming more solid like (again the weight hasn't increased). You only have to look at how much the boiled wort contracts when cooled to pitching temp (there is not less water its just more dense).
What holds true for sugars also holds true for proteins and for that matter lots of chemicals etc. This is true not only for solvated chemicals but also for particles in suspension (try the soil expt). Hydrometers are used to measure suspensions (same principle more able to resist the exerted force of the hydrometer).
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SteveD
