Displacer vs. hydrometer

[Mountaintop]

although not specific to still construction, this device is crucial to determine the start point, end points and final yields.
I use a home made displacer technique for determining specific gravity of our liquids in their "various states". I have used a hygrometer in the past but found it limiting in range, size and fragility. I would like to share what I use now because I've not seen it posted or discussed before. I can't take credit because it was likely Archimedes that invented it. It is robust,cheap and acurate. If others use a similar device I would like to here about your designs and methods.

[Bushman]

Do you have a picture of your displacer? I was always under the impression that a lot variables determine it's accuracy but I have never used one.

[Mountaintop]

For this to work you need ,
A) a suspended displacer of fixed volume
B) a sample to be tested in a small vessel
C) scales to measure the force difference.

Starting at the end...
C). some good quality digital scales to read 1/100 grams. My set was 12$ from china( includes shipping and tax) took 3 weeks ....but I was not in a hurry. Linearity is important , not accuracy. I also use this to measure jewellery, hops and yeast and for other brewing or around the house minutia.

B) this is best if it closely fits the displacer size. I found a sturdy old caper jar that is about 3" high and only an inch in diameter. This requires only a 40ml sample to get a good reading. If you sterilize first you can return the sample to the source.

A) this could be a lime on a string. But limes gain and lose weight with the weather so a rock on a string would be better. Rocks are hard to clean so I made mine using a short piece of 3/4" copper tube and a couple end caps. Silver Solder this up and add a short piece of copper wire as a hook to suspend it by.

[Mountaintop]

Now I did say "suspend". Meaning the displacer can not touch the jar ( sides or bottom) but must be fully submerged n the liquid. Originally I used a couple of water glasses and a pencil to hold it but I eventually upgraded to a couple pieces of bent wire and a support stand. I know it's getting all high tech and complicated now... But any time I can build stuff from what's kicking around ... It's a good day.

So here is the setup ready to run and dry.

[Mountaintop]

Calibration.
1) hang the displacer as shown in the last photO.
2) add water until the displacer is fully covered but not overly so.
3) remove the displacer.
4) mark the side of the vessel at the top of the liquid level with a big black sharpie line to indicate the "fill" line. You can sample a little above the line but don't under fill.
5) add cool tap water to the line.
6) zero (tare) the scales.
7) DRY OFF THE DISPLACER!!. Do this every time. (A couple of drops of moisture will throw off the reading. You can tell because the scales will be off the zero when you remove the displacer)
lower the displacer and suspend it by the structure. You can't just hold it. Even a surgeon will flinch to much to keep it steady.
9) record the reading. Say .. 29.03 grams. This is your baseline. Repeat steps 7 to 9 a couple of times to make sure you like your reference number. Right it down... It's water water weighs.

This sounds complex ...but once you are in the swing it gets fast and easy.

[Mountaintop]

Correction. Just reading this back...
7) place the jar with water sample on the scales. Zero (tare) the scales.

[goose eye]

Aint never seen one. Thanks for the schoolin

Ole boys use anti freeze checkers with marks

So I'm tole

[Mountaintop]

Yikes! That was step 6)

Must be getting late!
Tomorrow I'll post the "usage" tutorial?

Once you get used to the system. You can pour a shot, read it and drink it ...all under 15 seconds.
Hey. Something has to slow you down.

[Mountaintop]

Ok so now that We have a calibration number using water, we can compare that to any other sample. Specific gravity is just the comparison of what you have in the jar compared to that of water. If you know that your displacer reads 20.00 in water and your wort sample reads 21.00 then by dividing the two you get the relative difference ...aka the SG. So ..my sample/ water = SG
In the above...21/20= 1.050 this would be the SG of your sample of mash. Or 50 points.

Let me show you my real world example. My displacer reads 27.19 in water.( only did this once and wrote it down)
Tonight I measure my third cut of corn mash drippings and it reads 24.21. So now I divide the two ...(24.21/27.19=0.890 ). -Remember calibration value of water is always on the bottom of the equation-

I look this up on an online chart and find that
My SG is 70%. Or 140 proof.

After reading all of this back it sounds like a lot of work. "Might as well buy a hygrometer and just have it tell me the answer".


True enough. But, they are expensive,, ( limited range so you might need a few), need a reading fla$k , require a lot of fluid to check, can be hard to read the meniscus in foam or bubbly brew,are fragile and can be out of calibration.

I made myself a simple chart and printed it out so I did not need to do any conversion. This won't be any good to you because your displacer volume won't be the same as mine so it's just as an example.

Let me know if you need any clarification or help trying this out.
Cheers

[Mountaintop]

A couple of real important points.

-Always tare the scales before you lower in the displacer.
-Always make sure the displacer is dried off ( moist is ok but drops are not allowed back in)
- if the sample has a lot of co2 bubbles, take the reading quickly. Readings will slowly rise and become inaccurate as bubbles stick . Do it twice to be sure.

[Mountaintop]

This is great, what are the displacement numbers say from 100 proof compared to h2o?

Hey rock chuck, your numbers will be different than mine. If you look at my ref chart you will see (if it was me) I would need 25.40 to get 100 proof.

[skow69]

I look this up on an online chart

Mind telling us where to look for the chart?

[skow69]

What difference could it make if the displacer touches the sides or sits on the bottom?

[shadylane]

I'm scratching my head. What is a displacer?

[Tap]

Nice write up. Thanks for sharing. I have a scale that would be perfect for this.

I'm scratching my head. What is a displacer?

Read the post.

[badbird]

Nice idea! might give it a try.
Is that the 500g scales that you have there?

[Mountaintop]

What difference could it make if the displacer touches the sides or sits on the bottom?

Skow- it's very important.
Your trying to measure the weight that the displacer pushes on the liquid. Or it's bouncy. Touching the sides or bottom will add some portion of the mass of the displacer to the result. You only want the bouncy that the liquid exerts on the displacer - nothing else. If it touches the bottom then the weight of the displacer is included in the reading. If it has a thirty gram mass and sits on the bottom then the scale will read 30 grams every time regardless of the liquid density. Glass might as well be filled with air. Same result.

[Mountaintop]

I'm scratching my head. What is a displacer?

Haha. It's just any fixed volume that when lowered into a liquid will exert a bounty force. If the force is measured and the volume is known then the density of the liquid can be calculated.

Exactly the same as a hygrometer but instead of the slight change in force making it float higher or lower... You just measure the actual force (and do some light math).

[Mountaintop]

I hate this iPad spell corrector. A "bounty" force. Arrrggg.... Pirates and rum again.

- A buoyant force-

[shadylane]

I'm scratching my head. What is a displacer?

After the reading the responses, am I right in thinking, a displacer is a substitute for a hydrometer.
But what is the advantage

[NZChris]

But what is the advantage

Maybe because it won't break if you knock it over?

You're not restricted by the range of your hydrometer. Using this method, I should be able to measure cheese brine, distillate, brix, SG, OG, all with one tool.

I haven't tried it yet. I have the same scales in my apothecary and just need an appropriate dangler and frame to try this.

[skow69]

And a link to the online chart.

Or is it the one on the TTB site?

[Mountaintop]

But what is the advantage

Maybe because it won't break if you knock it over?

You're not restricted by the range of your hydrometer. Using this method, I should be able to measure cheese brine, distillate, brix, SG, OG, all with one tool.

I haven't tried it yet. I have the same scales in my apothecary and just need an appropriate dangler and frame to try this.

Exactly. It will do molasses to moonshine in one gadget. It also requires only a shot of booze to analyze where as the tall hygrometers require an equally tall graduated cylinder or need to float directly in the fermentor. They are also hard to read if the fluid levels a tiny bit foamy from the ferment.

As for the dangler...as mentioned I started with two water glasses and a pencil before I graduated to some bent welding rod stuck in plastic. Not sure if it's an improvement...but I don't risk breaking the glasses any more.

[Mountaintop]

I look this up on an online chart

Mind telling us where to look for the chart?

Example attached. You can find better quality picture.. searching "alcohol specific gravity"

image.jpg (25.58 KiB) Viewed 2785 times

[skow69]

Thanks for the thread. It's very helpful and informative. It will improve operations for many members, which is the whole point of the board. Kudos. Many thanks.

I hate to be the bitch,but I am one of those crazy people who think that words matter. A hygrometer is the thing in my humidore that measure humidity. The fragile thing that measures SG is a hydrometer. I read half of the first page wondering when you were going to bring humidity into the process.

Again, love the thread.

[Mountaintop]

Hey. Thanks for the correction. I knew it didn't exactly "feel right" when I was typing it.
I should have called it that fragile, floaty glass thing-Imy jig.

Best.

[InglisHill]

But what is the advantage

Maybe because it won't break if you knock it over?

You're not restricted by the range of your hydrometer. Using this method, I should be able to measure cheese brine, distillate, brix, SG, OG, all with one tool.

I haven't tried it yet. I have the same scales in my apothecary and just need an appropriate dangler and frame to try this.

Bring them over one day and we can make a stainless frame up

[12bolts]

A hygrometer is the thing in my humidore that measure humidity. The fragile thing that measures SG is a hydrometer. I read half of the first page wondering when you were going to bring humidity into the process.

I'm with skow here! Could a mod at least FIX the thread title

Cheers Phil

[NZChris]

I'm with skow here! Could a mod at least FIX the thread title

...and spoil our fun??

[Ferment_It]

Seems like a big benefit here is that temperature corrections are not necessary. If my memory serves me right temperature affects volume and density but not mass.

If this is true my parrot is gettin a new dangler.