Thanks for taking time to answer my question on a glaze called Louches Blue. It is a common glaze used at the Pullen Art Center Raleigh NC. A friend and I had the recipe, made it up, a 5 gallon bucket and when I used it it came out more brown than blue, which I hear is very common for this glaze to do, but at the studio it seems to break more blue than brown. I purchased a book by Bill Jones Cone 5-6 glazes and in it he had written that they take a bunch of left over glazes called "trash glaze" and mix them up and experiment with them...usually come out as a muddy brown and he added 2% titanium dioxide brought out the cobalt color. So, I added 2% titanium dioxide and it came out more green not blue. A three second dip came out a darker shade of green and then another 3 second dip made it break to a creamier whitish shade with the darker green under tones. I do like the beautiful color it came out but was expecting blue. Is it possible to get this glaze to come out blue now or is it to late? I don't feel it's a total loss since I like the color a whole lot better than the very dark brown. I am totally new to making glazes and went for it on this bucket since I thought the Louches turned out awful in the first place. Your help is greatly appreciated!!!
I'm glad to find this site and have a Guru to ask questions too! ;-)
Thank you for your recent question. As for reaching blue by pulling up the cobalt in a "trash glaze", this is only possible by chance. Slurry glazes are very unpredictable as they are a mixture of many different oxides and often result in unsatisfactory colors, such as muddy browns or flat chalky surfaces. What is even more disappointing is students or novice potters, such as yourself, tent to rely on these quick and often failed glaze techniques, instead of studying the chemistry of glaze formulation to get the exact results they desire. Using the methods above result in two very costly attributes. The first is often the loss of a beautiful piece of pottery as the potter will often rely on the technique and apply the glaze to finished pottery works instead of test tiles. And two, a great amount of time is lost in trying to figure out why a specific "trash glaze" is not working like the author said it would in the book. Although Mr Jones does have a point to using slurry glazes as a way to discover a temporary new glaze, it is just that, temporary, because once the glaze has been used up, it is impossible to reproduce it again without having it analyzed for the chemistry value.
Now to your question about the Louches Blue glaze. Without the recipe, I am unable to to determine the reason for the glaze breaking more brown than blue. Adding additional oxides, such as titanium dioxide to a glaze changes the chemical balance of the glaze percentages and therefore makes the glaze unreliable in future mixes.
Here is what I can tell you about your glaze. You stated in your question that the changes in application caused a change in color, i.e., first dip green, additional 3 second dip darker green and an additional 3 second dip whitish with green under tones. At this point, we know that the glaze application plays a big part on how the glaze reacts in the kiln. This is good to know as you can control the color by the application.
What we don't know is how the kiln affects the glaze. This is determined by testing the glaze using different firing techniques and adjusting the kiln during the firing. If the glaze is suppose to fire a blue color, then most likely, the atmosphere of the kiln is what is affecting the outcome of the color. In this, I am referring to the amount of oxygen entering the kiln.
Something that you will learn as you progress through glaze and firing over the years is that glazes are extremely dependent on the kiln they are fired in. For example, if you have a glaze that fires red in an oxidation kiln, such and an electric kiln, you can fire the same glaze in a reduction kiln, such as a raku kiln and it will fire black. Oxygen plays a big factor on the release of the oxides in a firing. Therefore, it is important to keep notes on how you fire so that you can achieve the same firing results each time when you have a successful firing.
The reason some potters don't keep firing records is because they either use electric kilns, which are commonly fired exactly the same each time, or they fire the same glaze patterns over and over, in which they memorize the firing procedure for the specific kiln they are using.
One suggestion I have for you is to remake the glaze without the additional titanium dioxide. Make a small batch of about 100 grams for testing. Use test tiles and record your procedure for application and firing. Since you didn't state what type of kiln you are firing in, I am assuming it is electric. However, if it is gas, it is important that you record the firing procedure used to fire the tiles.
Use 20 tiles, numbering them 1-10 two times. This means you will have two sets of tiles numbered 1-10, Apply the glaze in the following manner on each set. Tile one - apply 1 coat, tile two - 2 coats, tile three - 3 coats and so on. Place one set of tiles in the kiln near the wall and opposite the heat source. For instance, place them near the door of the kiln. Place the second set of tiles near the heat source or in the center of the kiln.
Fire the tiles with a normal firing procedure. When removing the tiles, make sure you keep the tiles together and label the tiles near the door or wall as COOL and the tiles near the heat source as HOT.
Examine each tile for the result you are looking for. If one tile gives you the results you want, then you have your answer, the number of applications and the location where the pottery must be placed in the kiln.
However, if the tiles do not give you the results, look for a tile that comes close by giving you some blue color. This tile will be the tile that you will use for the number of applications required on the pottery.
Next, determine if this was a COOL tile or HOT tile. If it was a COOL tile, then you know that the tile needs to be fired in a cooler temperature, possibly a cone lower to achieve the color you are looking for. If the tile is a HOT tile, you may need to soak the kiln to achieve the color you are looking for.
Unfortunately, when potters make up glaze recipes, they rarely give a good description on the firing technique to achieve the desired successful glaze. Testing is often the only way to determine how the glaze will react during different firing techniques. In this case, once you have determined a basis tile, you can then work on the firing technique to see if you can get the glaze to develop into the color you want. In this case, if the tile is a HOT tile and you need to soak the kiln, start with a 15 minute soak and increase your tests by 15 minutes until the color is achieved.
I know this is a lot of testing, however, if you achieve the color you want, it is all worth it in the end and you learn a lot about glaze application and firing control. In the future, never rely on a glaze as it is written. Always test it on a test tile before applying it to your work and make your own notes for future reference. Rewrite the glaze on note cards for your own records with your own firing technique notes and application description so that you can reproduce the glaze in the future.
As a final note, when looking for books on glazes, look for authors or potters who study in the chemistry of glazes, not just creating recipes. Understanding how oxides work together builds more successful glazes and more reliable glazes than those that are thrown together by chance. I am not criticizing any potter who does build glazes on a chance bases, however, if you want to learn about glaze design, you must hit the books and understand the chemistry behind it. Glazes are not like mixing paint. Red and yellow does not make orange. There are thousands of chemical makeups to glazes and thousands of ways to fire. Building your own glaze recipe designs, knowing your own firing techniques for each will help you understand how your glazes react to your clay and help you achieve the exact design and look you want for your pottery.
If you are looking to learn grad level chemistry in glazes, I teach online classes in the area. You are welcome to enroll in a free Orientation and Clay Bodies class to see if this might be an area where you would like to discover the chemistry of glazes and further your knowledge in pottery. I have been teaching these classes for over 25 years and brought them to online 10 years ago. They are very in depth, but progressive in nature so you are never lost as you learn. You can also take them at your leisure to prevent interruption of other activities. The web address is http://earthstokenfire.com/moodle/login/index.php
Create a new account and enroll in Orientation 101 to begin. Remember both Orientation 101 and Clay Bodies will be free classes to you.
If you would like to learn more about additional classes, you are welcome to visit my website at www.earthstokenfire.com Click on CLASSES link for more information.
I hope this has helped you. If you have further questions, please feel free to contact me at any time. I am always at your service.
Ms. Ti Phillips
Earth Stoke 'N Fire Pottery Studio and Artist Retreat