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Specific gravity


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#1 BRL

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Posted 30 April 2013 - 09:59 PM

I don't have a hygrometer and need to calculate the specific gravity of a glaze I am mixing. The glaze is premixed and I wasn't told how much water to add. If I measure 100 ml. In a container and mark the container at that level. Next add some water to glaze and stir well. Then sample the glaze in marked container and weigh. If the weight is 140 gms., isn't the specific gravity 1.40? Thanks for your help.

#2 Ben

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Posted 01 May 2013 - 12:21 PM

I don't have a hygrometer and need to calculate the specific gravity of a glaze I am mixing. The glaze is premixed and I wasn't told how much water to add. If I measure 100 ml. In a container and mark the container at that level. Next add some water to glaze and stir well. Then sample the glaze in marked container and weigh. If the weight is 140 gms., isn't the specific gravity 1.40? Thanks for your help.


That's correct so long as you are compensating for the weight of the container. I do it this way. I have even made myself counterweights for my triple beam balance for the containers I use so I don't have to do any math.
Ben

#3 BRL

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Posted 01 May 2013 - 03:01 PM


I don't have a hygrometer and need to calculate the specific gravity of a glaze I am mixing. The glaze is premixed and I wasn't told how much water to add. If I measure 100 ml. In a container and mark the container at that level. Next add some water to glaze and stir well. Then sample the glaze in marked container and weigh. If the weight is 140 gms., isn't the specific gravity 1.40? Thanks for your help.


That's correct so long as you are compensating for the weight of the container. I do it this way. I have even made myself counterweights for my triple beam balance for the containers I use so I don't have to do any

Thank you. Thought it was too easy where nothing seems easy.

#4 Diane Puckett

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Posted 01 May 2013 - 05:15 PM



I don't have a hygrometer and need to calculate the specific gravity of a glaze I am mixing. The glaze is premixed and I wasn't told how much water to add. If I measure 100 ml. In a container and mark the container at that level. Next add some water to glaze and stir well. Then sample the glaze in marked container and weigh. If the weight is 140 gms., isn't the specific gravity 1.40? Thanks for your help.


That's correct so long as you are compensating for the weight of the container. I do it this way. I have even made myself counterweights for my triple beam balance for the containers I use so I don't have to do any

Thank you. Thought it was too easy where nothing seems easy.

Near as I can tell, that is the easiest thing about making glazes. Assuming your scale is accurate.
Diane Puckett
Dry Ridge Pottery

#5 Frankiegirl

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Posted 01 May 2013 - 09:29 PM

I own a hydrometer and have never actually used it. I thought I would need it but I end up getting better results using my thumbnail as a gauge. Even with a hydrometer, you need to mix up a lot of glaze for it to be of any use. Good luck!

#6 trina

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Posted 02 May 2013 - 06:57 AM

I generally mix large amounts of glaze,and my hydrometre is a 500 ml measuring cup with a hole in the bottom and a stop watch. Call me crazy..

#7 OffCenter

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Posted 02 May 2013 - 08:15 AM

I think I still have a tube hydrometer somewhere, but the one that grew naturally at the end of my arm is more accurate and always handy.

Jim
E pur si muove.

"But it does move," said Galileo under his breath.

#8 BRL

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Posted 02 May 2013 - 10:16 AM

I think I still have a tube hydrometer somewhere, but the one that grew naturally at the end of my arm is more accurate and always handy.

Jim

So, glaze runs off nail or glaze runs out of the container in so many seconds or glaze covers your hands like cream. Please explain, and thanks.

#9 OffCenter

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Posted 02 May 2013 - 10:54 AM


I think I still have a tube hydrometer somewhere, but the one that grew naturally at the end of my arm is more accurate and always handy.

Jim

So, glaze runs off nail or glaze runs out of the container in so many seconds or glaze covers your hands like cream. Please explain, and thanks.


It's very simple. After mixing and stirring and applying glazes by hand thousands of times, I can adjust a glaze just right for dipping or spraying by watching it slide off my hand. I think most potters can. For me, using a hydrometer would be like using a carefully calibrated onager to put a basketball through the hoop instead of just taking the shot.

Jim
E pur si muove.

"But it does move," said Galileo under his breath.

#10 trina

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Posted 02 May 2013 - 11:07 AM



I think I still have a tube hydrometer somewhere, but the one that grew naturally at the end of my arm is more accurate and always handy.

Jim

So, glaze runs off nail or glaze runs out of the container in so many seconds or glaze covers your hands like cream. Please explain, and thanks.


It's very simple. After mixing and stirring and applying glazes by hand thousands of times, I can adjust a glaze just right for dipping or spraying by watching it slide off my hand. I think most potters can. For me, using a hydrometer would be like using a carefully calibrated onager to put a basketball through the hoop instead of just taking the shot.

Jim


ONAGER now thats a word....;)

#11 trina

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Posted 02 May 2013 - 04:36 PM

Jim, have you been to Randel's restaurant in Lafayette? My very good friend was just there on business from the UK. Apparantly they have very good crawfish. Just thought you must be pretty near.... T

#12 OffCenter

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Posted 02 May 2013 - 05:07 PM

Jim, have you been to Randel's restaurant in Lafayette? My very good friend was just there on business from the UK. Apparantly they have very good crawfish. Just thought you must be pretty near.... T


Never been. Not really very close to it. I'm located in the middle of the state near Macon, also known as The Heart of Darkness. Beautiful area there in the nw corner of GA. Thanks. I'll make a note of it. I love crawfish in grits!

Jim
E pur si muove.

"But it does move," said Galileo under his breath.

#13 Pres

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Posted 03 May 2013 - 06:29 AM


Jim, have you been to Randel's restaurant in Lafayette? My very good friend was just there on business from the UK. Apparantly they have very good crawfish. Just thought you must be pretty near.... T


Never been. Not really very close to it. I'm located in the middle of the state near Macon, also known as The Heart of Darkness. Beautiful area there in the nw corner of GA. Thanks. I'll make a note of it. I love crawfish in grits!

Jim


Macon GA. Know it well, I used to live in Warner Robbins. Five years there while dad was stationed. This was 61-66.

Simply retired teacher, not dead, living the dream. on and on and. . . . on. . . .                                                                                 http://picworkspottery.blogspot.com/


#14 OffCenter

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Posted 03 May 2013 - 08:52 AM



Jim, have you been to Randel's restaurant in Lafayette? My very good friend was just there on business from the UK. Apparantly they have very good crawfish. Just thought you must be pretty near.... T


Never been. Not really very close to it. I'm located in the middle of the state near Macon, also known as The Heart of Darkness. Beautiful area there in the nw corner of GA. Thanks. I'll make a note of it. I love crawfish in grits!

Jim


Macon GA. Know it well, I used to live in Warner Robbins. Five years there while dad was stationed. This was 61-66.


Somebody's gonna come down on us for getting so far off topic but -- Small world, Pres! I was in high school then. I'm guessing you were, too. Lots of changes were going on in Middle Georgia during the years you were here.

Jim
E pur si muove.

"But it does move," said Galileo under his breath.

#15 Frankiegirl

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Posted 03 May 2013 - 10:49 AM


I think I still have a tube hydrometer somewhere, but the one that grew naturally at the end of my arm is more accurate and always handy.

Jim

So, glaze runs off nail or glaze runs out of the container in so many seconds or glaze covers your hands like cream. Please explain, and thanks.


I think this is something you need to practice -besides that some glazes are better thick or thin. If you have a glaze that is mixed to the right moisture level, test it out so you can compare when you recreate it. You need to be able to see what it looks like on your thumb because it is difficult to explain. There must be a youtube video about this.

For me, some of my glazes are best when they look like heavy whipping cream consistency and when I dip my thumb in, I can still see the separation line at my cuticle through the glaze. If it looks thicker like I dipped it in paraffin, it is too thick. If it is thinner like whole milk, it is too thin. Other glazes are best more like runny yogurt consistency though, so you need to know your glazes. Hope that makes sense.

#16 Celia UK

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Posted 03 May 2013 - 02:10 PM

I started with the 'single cream' thickness in mind, but this was generally too thick for my glazes, so I now think 'milk'. It could be that single cream thickness is different in UK. Also, yoghurt comes in so many thicknesses, that this really doesn't help at all. Test, test, test ....as everyone keeps saying. No short cuts here.




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