Hydrometers For Earthenware Glaze

[granny potter]

Does anyone out there use a hydrometer on your glazes? When I ordered one it did not even come with instructions so I would like to know what the density of earthenware glaze should be.

[Guest JBaymore]

Does anyone out there use a hydrometer on your glazes? When I ordered one it did not even come with instructions so I would like to know what the density of earthenware glaze should be.

 

 

 

GrannyPotter,

 

Hi.

 

I think you'll find that you get better results in maintaining glaze slurry consistency by using a viscometer rather than a hydrometer. The typical values for glaze suspensions are not easy to measure accurately with a hydrometer. And the hydrometer misses some "variables" that are important to glaze application.

 

You can make a "personal" hydrometer very easily. If you don't need to compare to industrial standards directly... this will work just fine.

 

Get an empty metal soup can. Drill a 1/4" to 3/8" hole in the center of the bottom, and smooth off the rough edges with silicon carbide paper. With a sharpie type marker, draw a line on the inside of the can about 1/2" down from the top surface.

 

Now you need to get a batch of glase mixed up to the exact consistency that you like to have for application. When it is perfect for YOUR application techiques and the nature of YOUR particluar clay body and YOUR bisque temperature........ you need to create a "standard" for yourself. The standard unit here is TIME.

 

So you'll need a stopwatch. The function on most digital watches is absolutely fine.

 

Stir up that glaze you want to test well. Get enough to fill the metal can viscometer you made in a separate pouring cup. Put your finger tightly over the hole in the bottom of the can to seal it. Pour the glaze into the can up to the line.

 

Now release the finger over the hole and start the stopwatch at the same time. The instant the glaze stops flowing as a stream out of the hole, stop the watch.

 

If you mix the new batches of the glaze to match this measured time.... they will apply the same. Far better than the hydrometer reading alone will do. You need to create a "flow time standard" for each of your glazes, and then keep that home-made can viscometer in a safe place for future testing.

 

For matching to industrial numbers, there are specific dimensions for the viscometer. You can go that route if you want to; most potters don't need this.

 

best,

 

......................john

[azjoe]

For many, dipping the thumbnail is sufficient test, others prefer the accuracy of the viscometer, and others are satisfied with the hydrometer. Each method has its own set of merits/limitations. The Laguna website recommends mixing their glazes as follows:

 

The hydrometer reading should be approximately

• 55 for color dipping glazes
• 46-47 for clear dipping glazes
• 60 for spraying
• 65 for brushing

I find this sufficient for many (but not all glazes). Regardless of the method you choose, you'll need to tweak each of the problematic glazes for best results. Once you find what works best for you, write it down so you can repeat your successes.

[granny potter]

 

[

 

quote name=JBaymore' date='29 August 2010 - 10:10 AM' timestamp='1283094608' post='2299]

 

Does anyone out there use a hydrometer on your glazes? When I ordered one it did not even come with instructions so I would like to know what the density of earthenware glaze should be.

 

 

 

GrannyPotter,

 

Hi.

 

I think you'll find that you get better results in maintaining glaze slurry consistency by using a viscometer rather than a hydrometer. The typical values for glaze suspensions are not easy to measure accurately with a hydrometer. And the hydrometer misses some "variables" that are important to glaze application.

 

You can make a "personal" hydrometer very easily. If you don't need to compare to industrial standards directly... this will work just fine.

 

Get an empty metal soup can. Drill a 1/4" to 3/8" hole in the center of the bottom, and smooth off the rough edges with silicon carbide paper. With a sharpie type marker, draw a line on the inside of the can about 1/2" down from the top surface.

 

Now you need to get a batch of glase mixed up to the exact consistency that you like to have for application. When it is perfect for YOUR application techiques and the nature of YOUR particluar clay body and YOUR bisque temperature........ you need to create a "standard" for yourself. The standard unit here is TIME.

 

So you'll need a stopwatch. The function on most digital watches is absolutely fine.

 

Stir up that glaze you want to test well. Get enough to fill the metal can viscometer you made in a separate pouring cup. Put your finger tightly over the hole in the bottom of the can to seal it. Pour the glaze into the can up to the line.

 

Now release the finger over the hole and start the stopwatch at the same time. The instant the glaze stops flowing as a stream out of the hole, stop the watch.

 

If you mix the new batches of the glaze to match this measured time.... they will apply the same. Far better than the hydrometer reading alone will do. You need to create a "flow time standard" for each of your glazes, and then keep that home-made can viscometer in a safe place for future testing.

 

For matching to industrial numbers, there are specific dimensions for the viscometer. You can go that route if you want to; most potters don't need this.

 

best,

 

......................john

 

 

Thanks, great info!

[granny potter]

For many, dipping the thumbnail is sufficient test, others prefer the accuracy of the viscometer, and others are satisfied with the hydrometer. Each method has its own set of merits/limitations. The Laguna website recommends mixing their glazes as follows:

 

The hydrometer reading should be approximately

• 55 for color dipping glazes
• 46-47 for clear dipping glazes
• 60 for spraying
• 65 for brushing

I find this sufficient for many (but not all glazes). Regardless of the method you choose, you'll need to tweak each of the problematic glazes for best results. Once you find what works best for you, write it down so you can repeat your successes.

 

 

Appreciate the info.

[Deb Evans]

Just a note:

there are some other variables to consider.

If you soft bisque ^ 08 - glaze needs to be a bit thicker so you get good coat in 1 dip, if you are just going for total coverage of 1 glaze.

If bisquing at higher ^04 temp than you can go w/thiner consistantcy.

For most of the glazes I use in mid range and raku , I 've always just dipped my finger in bucket, if the glaze is mcdonald milkshake consistency = perfect.