[Bluegeckopottery]

Some out there

Please help me . How do I get my glazes the density. Thanks

[neilestrick]

I'm not super picky about the viscosity of the glazes in my studio. I check them regularly to make sure they're not too thick, but I do not use a hydrometer because I do not have the time to deal with it, and have not found it to be necessary. I eyeball them to a creamy chocolate milk consistency. My students are instructed to dip their pots for a count of 6 to get the glaze the right thickness. Our count is a little fase than seconds, but about 5 seconds would be close. As they learn to use the glazes they will often go a little thicker to get them to run more, but the 6 count provides a consistent baseline from which to experiment. For the second dip, they do a 4 count. No more than a total of 12 is allowed, or the glaze will be too thick and either start to crack and flake before firing, or run too much in the firing.

[catpaws]

I use my eye and if the glaze seems like single cream then it's usually ok. Not very scientific I know but you get to know our glazes the more you use them. Try doing a series of test pieces and keep a note of the consistency of them. Failing that I saw there was a dvd available on the 4th May ceramic daily site which seemed foolproof.

[icyone]

I use a DuPont viscosity checking cup. Basically I just time how long till the ladle full of glaze runs through it. My glaze is very picky and I have to get it withing a second of my preferred 19 second range.

You can make a home made one pretty easy once you have a good batch to refer to.

here is the tool I use

[Ben]

Viscosity cups will measure viscosity which is not the same as specific gravity though it can be a very important factor in how a glaze behaves during application.

Here's how I measure specific gravity.
I bought a cheap plastic 100ml graduated cylinder on the 'net. It was like $3US.
put the dry, empty cylinder on your triple beam balance and zero the balance.
Stir your glaze and pour 100ml into the cylinder then weigh on your triple beam balance.
Should weigh something MORE than 100 grams since 100 ml water = 100 grams
if it weighs 150 grams then the SG(specific gravity) is 1.50

Most of my cone ten glazes work best between 1.35 and 1.50 SG but so much depends on how your whole process. Each clay and glaze will be a little different. Heck individual shapes of pots make require some added water to keep the glaze from going on too thick. You'll have to figure out what SG works for your glazes/ware BUT this method will get you a repeatable starting point.

If you want to get even more since lab-ish, do this. Make some test tiles and get a quart of your glaze. Measure the SG of your quart then Let the glaze settle out and pour off some of the water (keep it).
Now measure the SG. Dip a tile. Mark the Sg on the tile. add some water, measure SG, dip and mark the tile etc etc etc until you have added all your water back in.
Fire the tiles and then you'll have lots of info for THAT glaze. It may look better thin on one clay and thick on another.
Hope this helps!
NOW, go make some test tiles!

[Agatha X.W. Gao]

you can use a small test piece first, then put the glaze on your works.
usually if we put too much water in glaze, we will spread it several times, or we just spread it once.

[Mark C.]

Buy a glaze hydrometer and you will never have this issue again.Its a glass tube about a foot long with graduations on the inside.
Mark

[scoobydoozie]

Speaking of dipping.... I just bought Duncan's Pure Brilliance dipping clear. Used a viscosity cup and added water to get it to 25. When I remove my dipped piece from the bucket, their were lots of little pinholes where the glaze did not stick. (This is before firing). Did I get to many air bubbles in my glaze before I dipped? I used a drill with a paint mixer. How do I fix the piece?

[Mark C.]

scoobydoozie, on 07 June 2012 - 07:14 AM, said:

Speaking of dipping.... I just bought Duncan's Pure Brilliance dipping clear. Used a viscosity cup and added water to get it to 25. When I remove my dipped piece from the bucket, their were lots of little pinholes where the glaze did not stick. (This is before firing). Did I get to many air bubbles in my glaze before I dipped? I used a drill with a paint mixer. How do I fix the piece?

Mixer was fine-just wait a few minutes next time and use a stick for final stiring.
As far as the tiny bubbles-when the glaze dries just rub them out with your hand carefully then fire the piece..
Mark

[Red Rocks]

Mark C., on 06 June 2012 - 03:58 PM, said:

Buy a glaze hydrometer and you will never have this issue again.Its a glass tube about a foot long with graduations on the inside.
Mark

Mark:

Different glazes are optimum at different viscosity levels, using a hydrometer how do you utilize it to measure the correct viscosity of say a copper red versus a matt white? I agree that a hydrometer is an easy and efficient method, I have just never understood how you determine the correct level for each glaze.

As always, thanks for sharing your expertise.

[JBaymore]

In my experience, viscosity is a much more important property of glaze slurries than the specific gravity. It tells more abnout how the slurry will actually apply. It combines the issue of specific gravity with that of rheology. Industry relies heavily on viscosity.

Also at the typical SGs of glaze slurries, it is my understanding that the standard hydrometers lose their accuracy.

best,

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

[JBaymore]

Red Rocks, on 08 September 2012 - 04:18 PM, said:

Different glazes are optimum at different viscosity levels, using a hydrometer how do you utilize it to measure the correct viscosity of say a copper red versus a matt white? I agree that a hydrometer is an easy and efficient method, I have just never understood how you determine the correct level for each glaze.

Through testing with the specific glazes. You mix glazes to different test values (either SG or Viscosity or ????) and then apply the glazes in a highly standardized way to the actual clay bodies that you are going to use. Record the tests, record the results. Decide which mix works the way you want.

best,

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

[Mark C.]

I agree about the various ways to measure the right water content. I use viscosity for all slip measuring and thats works well for me. I learned the hydrometer for glazes and am dialed in with it now after all these years-I do use a new one every 5-10 years as I break them now and again-I could learn viscosity for glazes but if its not broke I'm not fixing it.
I have learned the various reading for most of my glazes simply by testing trail and error. I write the measurement on the side of bucket. Some glazes are very touchy others not so much.
I originally learned this by how it ran of my hand-(back in early 70's) and since mid late 80's I always wear latex gloves when glazing so thats not an option anymore.
Most of my glazes run around the 1500 -1550 mark on one of the scales. I made a plastic tube so I can measure smaller amounts as well.If I can I'll take a photo and post a new thread on this.
Big shows coming up soon spare time is short.
Mark

[yedrow]

We have something like 17 glazes in use at any one time. They vary considerably in their behavior/rheology. I've found that no one method works. The problem with the hydrometer and viscometer (cup with a hole in the bottom style) is that the viscosity of the glazes covers a pretty wide range. We have a very viscous glaze that a hydrometer won't move in, and it heaps up so bad that you can't use the 100ml trick to get the specific gravity. We have another glaze that is, I'm guessing, so thixotropic that when you dip a series of smaller objects in it, the stuff won't stop sloshing and it's hard to get a level line (one color top, another bottom, example). There is a lot to be said for testing glazes and matching that to visual/physical observations, along with measurements.

Joel.

[Mark C.]

Mark C., on 08 September 2012 - 08:11 PM, said:

I agree about the various ways to measure the right water content. I use viscosity for all slip measuring and thats works well for me. I learned the hydrometer for glazes and am dialed in with it now after all these years-I do use a new one every 5-10 years as I break them now and again-I could learn viscosity for glazes but if its not broke I'm not fixing it.
I have learned the various reading for most of my glazes simply by testing trail and error. I write the measurement on the side of bucket. Some glazes are very touchy others not so much.
I originally learned this by how it ran of my hand-(back in early 70's) and since mid late 80's I always wear latex gloves when glazing so thats not an option anymore.But I can stll do this as its like riding a bike years later.
Most of my glazes run around the 1500 -1550 mark on one of the scales. I made a plastic tube so I can measure smaller amounts as well.If I can I'll take a photo and post a new thread on this.
Big shows coming up soon spare time is short.
Mark

Sorry i hit the wrong button while in edit mode