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using hydrometer


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#1 Val

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Posted 03 January 2013 - 10:34 AM

I hope you all are not sick of newbie questions ! I am always in a quandary over the amount of water to add to dry glaze. So far I have just dipped scraps of bisque and added more water until it seemed right........ Now I bought a hydrometer, and a paint viscosity cup but how do I use them? No instructions came with. Also, I read that hard or soft water can make a difference. Do you use tap water, or distilled water for glaze mixing?

#2 Mark C.

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Posted 03 January 2013 - 11:59 AM

Val
I use my well water as thats my supply source of all water-but tap water is fine.
As far as the hydrometer wet it 1st always before use in clean water and then use when wet-or you can always use it dry but it must be dry every time-I use mine wet as it easier than drying ever dip.
Many of my glazes are tuned in around 1600-1550-1520. That should be a starting point.
The cup is filled to a given line or full and the time it takes to empty is recorded-(time this with a accurate timer)
I have only used the cup with slip so someone else can elaborate.
Mark
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#3 Val

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Posted 03 January 2013 - 03:37 PM

I found this good article as far as viscosity http://www.baileypot...cosityguide.htm however they say 40 to 60 seconds to empty a viscosity cup is good while several other articles I read say 18 to 20 seconds. That's quite a difference ! Waaa!

#4 Mark McCombs

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Posted 03 January 2013 - 04:11 PM

Viscosity readings for me are between 16 and 20 seconds (Dupont cup 50)

If you have a hydrometer, I would start there and test your glazes from 1.3 sp to 1.6 sp.

Your dipping times will vary depending on absorbency of the bisque ware (porosity and thickness)


:-)
Mark
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#5 bciskepottery

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Posted 03 January 2013 - 05:22 PM

I found this good article as far as viscosity http://www.baileypot...cosityguide.htm however they say 40 to 60 seconds to empty a viscosity cup is good while several other articles I read say 18 to 20 seconds. That's quite a difference ! Waaa!



May depend on the size of the hole in the cup . . . bet there is no standard.

#6 Mark C.

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Posted 03 January 2013 - 06:46 PM

One last note on hydrometers-there are several different types.
Mark
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www.liscomhillpottery.com

#7 yedrow

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Posted 04 January 2013 - 12:38 AM

I always take mine to the first line and drop it from there. If the glaze is too viscous I tap the side of the container until it quits moving. There is no perfect studio way to accurately measure the sg/viscosity of a glaze, so don't be real freaky about it (like I did). Once you get comfortable with a glaze you can probably get close enough just eyeballing it by dipping your fingers in and letting it move on your hand.

Joel.

#8 Ben

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Posted 04 January 2013 - 01:17 PM

I think that measuring SG by weighing a set volume of glaze is more accurate.
Get a plastic 100ml graduated cylinder (usually under $5). Weigh it on your gram scale. Make an appropriate tare weight or just write the mass of the cylinder on the base with sharpie.
Stir glaze well and fill the cylinder with 100 ml of glaze. Weigh the whole kit and kaboodle. Either use the tare weight or subtract the weight of the cylinder.
The remaining weight in grams is the SG once you move the decimal 2 places left (ie 145gr =1.45SG)

My 2 cents.
Ben

#9 jlawson

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Posted 04 January 2013 - 04:05 PM

Hi Val,

The hydrometer and the paint pot are both good simple ways of measuring the viscosity of your glaze. However, the thinness or thickness of the glaze isn't dependent upon strictly the amount of water that it has in it. It is also important to know if your glaze is acidic or base, and it's good to know how to adjust the situation with that glaze. One of the clearest explanations of this situation is a You Tube video by John Britt. Here is the address for this video. I'm sorry that I haven't figure out yet how to actually post a link within the text. So here it is, just copy and paste this to your browser and you should be able to get there.

I hope this helps.

Jim

#10 johnb

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Posted 05 January 2013 - 12:15 AM

Val, View John Britt on 'you-tube' he provides a very good explanation for your questions as was suggested by jlawson. It was posted in Dec. 2012. Good luck. John

#11 yedrow

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Posted 05 January 2013 - 12:49 AM

The problem with weighing the glaze is the difficulty in accounting for the meniscus (Meniscus Wiki). If you could do 1000g accurately then the larger volume would absorb the few grams margin of error and be only a small percentage of it. However, with 100g, the percentage of error can be pretty high.

You can order a 250ml glass cylinder from Amazon for a few bucks. With that you only have to take out a little glaze and you can use your hydrometer. You only need little over 200ml to do it. If the glaze is particularly viscous just tap the side until the hydrometer quits sinking. Your results should be fairly reproducible.

Joel.

#12 Val

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Posted 05 January 2013 - 04:55 PM

Ah heck, the more I learn , the more confused . I'm not yet making my own glazes, so how do I know if they are acid or base? Buy ph strips? The UTube was definitely informative.

#13 yedrow

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Posted 06 January 2013 - 01:09 AM

I don't think the changes in ph are very big. Just remember that you can get a glaze wetter by adding water, but that the bisque has to hold that water. A properly flocculated glaze will help you avoid using too much water. Then, watch Brit's video. He explains it well.

Joel.




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