Making a hydrometer

I dont want to buy a hydrometer, so I was thinking of making one. My idea is to take a straw, heat one end and close it, then put some sort of weight inside the straw. To make the marks I would put the straw in distilled water and where it floats that would be 1. Then I make a mark were the one is. To make acurate marks I print out a actual size ruler, cut it out and put it inside the straw. Would this work? Another question, are hydrometers in inches or centimeters?

hydrometers aren't in inches or centimeters. they are in units of density, such as Brix/Degrees Plato/SG. You would need a solution of known density, for instance 1.10 SG, and use that to mark the high end of your homemade hydrometer.

I cant think of any reason to DIY this instrument that costs $6.50 from most supply stores...

Hydrometers are priceless. Just buy one.
To be able to properly calibrate a diy one would involve buying one any way.

It would be pretty expensive to import one to the Dominican Republic apparently.

It would be interesting if it could be done easily though, especially if it could be made of plastic. No more broken ones.

Revvy said:

It would be interesting if it could be done easily though, especially if it could be made of plastic. No more broken ones.

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I would think you would have real issues using it in a typical hydrometer tube, it just going to float over and stick to one side. Or at least that's what I envision happening.

But if you were chucking it right into a fermenter, then I think there's no reason this couldn't be reasonably accomplished.

I theory, you could make one, but they are pretty inexpensive. I think to make it work properly, you would need to find 1.000 (distilled water at 60 degrees F) AND have to find 1.100 (not sure how you would find that without some sort of control). Then you could make equal increments between the two initial readings. But I still dont think this will be very reliable

I am fairly certain you will have better luck measuring the mass and volume and calculating the specific gravity. Sg is simply density of the substance divided by the density of water. A scale good for measuring hops would be accurate enough I think, and then you just need a container you can fill with wort to the exact same level every time, or a graduated cylinder.

So to find the sg I just need to find the density of what I am fermenting , since the density water's density is 1 g/mL. The scale I have measures grams with no decimals, is that ok for finding sg?

Isometric said:

So to find the sg I just need to find the density of what I am fermenting , since the density water's density is 1 g/mL. The scale I have measures grams with no decimals, is that ok for finding sg?

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Depends on what kind of volume you're talking about. If you are measuring 10 mL and your mass is only in full grams, then no, that's not as accurate as you want. If you're measuring the mass of 1000 mL, then accuracy to the gram is fine. But really it all just depends on how much accuracy you want.

EDIT: Edited cuz of bad math.

I would even say 500ml should be good enough, +-2 gravity points

Bobby_M said:

It would be pretty expensive to import one to the Dominican Republic apparently.

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But getting all the other stuff one needs to brew is a snap?

I think it's just one of those idle thoughts that people often have here on HBT. Trying to DIY something that is cheap, robust, and readily available seems to be a common subject here.

USPS first class shipping is only $5 from the states. I have an extra cooper's hydrometer if you're interested. It cost me $10 + $5 to get it shipped to me.

Coopers Beer Making Accessories > Beer Hydrometer

LordUlrich said:

and then you just need a container you can fill with wort to the exact same level every time, or a graduated cylinder.

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what you want is called a pychnometer, and its essentially a glass flask of known weight and very precise volume. you fill the container to the very top with liquid, then put the glass stopper into it so there are no air bubbles. this gives you a very accurate volume measurement. then you just weigh the whole thing and subtract the container's weight.

audger said:

what you want is called a pychnometer, and its essentially a glass flask of known weight and very precise volume. you fill the container to the very top with liquid, then put the glass stopper into it so there are no air bubbles. this gives you a very accurate volume measurement. then you just weigh the whole thing and subtract the container's weight.

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That would certainly do it. But I wager that anyone who didn't want to buy a hydrometer also wouldn't want to buy a pychnometer.

That's a neat looking device tho. I've not seen one of those before.

To Make and Calibrate a Homemade Hydrometer
Need: Chewing Gum, Drinking Straw, Distilled Water, Sugar
1) Chew Gum and put on one end of straw so that it is airtight
2) Measure out 100 ml of water and place the hydometer in marking the waterline as 0 °Bx or a specific gravity of one
3) Remove hydrometer and add 1 g sugar to distilled water and repete this time marking as 1 °Bx
4) Repeat until you reach desired °Bx (25 is a specific gravity of 1.1057 or 15%)
(Edit) SG = (Brix / (258.6-((Brix / 258.2)*227.1))) + 1

http://m.wikihow.com/Build-a-Hydrometer try this method.