Cathy Elliot on fri 18 apr 08
I am in the process of making some tiles for the hearth of my fireplace. I made the tiles by rolling
them out with my bailey mini slab roller. I have quite a few of them. I have decorated them with
Amaco velvet underglazes, and bisque fired them to cone 06. Now for the problem: today I was on
the web, and discovered a wonderful site, at http://www.brackers.com/product_info/amg_v_series.cfm
It is most unfortunate that I had not discovered this site before I painted my tiles!!! I say this,
because I got information from this site that was not available from anywhere else! One of the
underglazes, Terra Cotta, to be exact, apparently totally changes color when fired to Cone 5, and
covered with a transparent gloss glaze---which is exactly what I had planned to do! So now, I am
in a real mess. I have a lot of tiles. Most of them will be okay, fired to the maturity of my clay
body, which is cone 5--but a whole bunch are decorated with V-303 Terra Cotta, which they say
will fade away when glazed over and fired to Cone 5.
My question is: can I just put a glossy transparent glaze on these tiles, and glaze fire them to Cone
06? I know that is NOT the maturing temperature of the clay, but does it really matter if the tiles
are just going to be installed on a fireplace hearth? Of course, they do not need to be water
tight.... Also, should I glaze fire ALL the tiles to 06 instead of firing some to maturity, and others
to the lower temperature because of different shrinkage?
Sorry about the newbie question, but I have spent a lot of time on this project, and would like to
save it!
Steve Mills on fri 18 apr 08
Dear Cathy,
Go ahead.
Reward Velvet colours contain some flux so will be almost like a matt glaze and non-smearing at 06. They'd be better at 04 or 03 as the clay will be a bit stronger, but ok at 06.
Good luck
Steve
Bath
UK
Cathy Elliot wrote:
I am in the process of making some tiles for the hearth of my fireplace. I made the tiles by rolling
them out with my bailey mini slab roller. I have quite a few of them. I have decorated them with
Amaco velvet underglazes, and bisque fired them to cone 06. Now for the problem: today I was on
the web, and discovered a wonderful site, at http://www.brackers.com/product_info/amg_v_series.cfm
It is most unfortunate that I had not discovered this site before I painted my tiles!!! I say this,
because I got information from this site that was not available from anywhere else! One of the
underglazes, Terra Cotta, to be exact, apparently totally changes color when fired to Cone 5, and
covered with a transparent gloss glaze---which is exactly what I had planned to do! So now, I am
in a real mess. I have a lot of tiles. Most of them will be okay, fired to the maturity of my clay
body, which is cone 5--but a whole bunch are decorated with V-303 Terra Cotta, which they say
will fade away when glazed over and fired to Cone 5.
My question is: can I just put a glossy transparent glaze on these tiles, and glaze fire them to Cone
06? I know that is NOT the maturing temperature of the clay, but does it really matter if the tiles
are just going to be installed on a fireplace hearth? Of course, they do not need to be water
tight.... Also, should I glaze fire ALL the tiles to 06 instead of firing some to maturity, and others
to the lower temperature because of different shrinkage?
Sorry about the newbie question, but I have spent a lot of time on this project, and would like to
save it!
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Christine Campbell on fri 18 apr 08
Cathy -
I am going to recommend that
you STOP right now
and do some tests.
Take your leftover clay and make
some test tiles. Try all of your
solutions on these disposable
items, not on the good ones.
This will give you a better idea
of what happens and what you'll like.
Try different formulas of clear glazes
to see which one causes less color change ...
it might be as simple as just
painting over the designs with
another underglaze color that does not fade.
TEST before you go any further.
Good Luck
Chris Campbell - in North Carolina
back from cyber waste lands !!
Chris Campbell Pottery LLC
9417 Koupela Drive
Raleigh NC 27615-2233
Designs in Colored Porcelain
1-800-652-1008
Fax : 919-676-2062
website: www.ccpottery.com
wholesale : www.wholesalecrafts.com
Paulette Carr on sat 19 apr 08
Cathy Elliot wrote:
My question is: can I just put a glossy transparent glaze on these
tiles, and glaze fire them to Cone
06? I know that is NOT the maturing temperature of the clay, but does
it really matter if the tiles
are just going to be installed on a fireplace hearth? Of course, they
do not need to be water
tight.... Also, should I glaze fire ALL the tiles to 06 instead of
firing some to maturity, and others
to the lower temperature because of different shrinkage?
Chris Campbell wrote:
Cathy -
I am going to recommend that
you STOP right now
and do some tests.
...
TEST before you go any further.
Cathy,
I make tiles, and have been doing this for over 12 years. No, you
cannot use these tiles, under-fired to ^06, on your hearth... they
will be too weak and fragile, and you will get crazing as these very
porous, underfired tiles absorb moisture from the air overtime, if
they do not craze immediately. Crazing further weakens the clay.
This would be OK if it were just sculpture, but not for architectural
purposes - and your hearth is architectural. If you use a low-fire
clay that matures, these earthenware tiles will be stronger and more
appropriate then using an immature bisque tile, and the low-fire
glazes should fit better, yielding a stronger tile. The tiles that
you have made should be fired to maturity (^6?) for strength.
I am going to agree with Chris Campbell. You need to test first, as
very little of this is straightforward and intuitive. I have often
been surprised when what came out of the kiln did not match my
expectations, or others samples and descriptions (especially
commercial glaze producers). With a relatively small time
investment, you will get what you want, without having to settle for
an inferior, weak product. Remember, ceramic tile is not just the
surface decoration... there is an integrity in the strength and
durability, and all of this takes a little time to develop.
One word of warning for tiles: if you do not have enough grog in the
clay body, you may (read I really struggled with this for a long
time) see warping and cracking. Testing will reveal this to you.
Good luck!
My best,
Paulette Carr
Paulette Carr Studio
St. Louis, MO
Member, Potters Council
Snail Scott on sat 19 apr 08
> Date: Fri, 18 Apr 2008 01:30:18 -0500
> From: Cathy Elliot
> ...tiles for the hearth of my fireplace...One of the
> underglazes, Terra Cotta, to be exact, apparently totally changes
> color when fired to Cone 5, and
> covered with a transparent gloss glaze...can I just put a glossy
> transparent glaze on these tiles, and glaze fire them to Cone 06?...
First: Do a test! A project of this magnitude should
never be executed with materials you've never used
before (or not used in the same way). When most
folks decide to do a great big architectural project,
they might measure the site where the work will fit,
do preliminary sketches or maquettes, and test the
clay's shrinkage, not relying on published numbers
but actual results in their own kiln. After all that, not
testing thier proposed surfaces could make all that
other work (not to mention the actual execution)
totally wasted. It's such a little, easy thing!
Water under the bridge - I'm not gonna berate you
for what you should have done, but it's not too late
to do that testing now! If it's only been bisque-fired
or is still green, you can find a stable underglaze
for your midrange temperature, and cover up the
one that won't work. (Test this, too! -both the new
underglaze, AND how well it will cover the first.)
In fact, step back a moment, and do some test
pieces, using the same painting techniques you
used on the real thing, to see how it will work out.
Test it with your proposed clear glaze, but leave
some pieces to test with other clears - different
recipes can affect underglazes very differently.
And if you are pretty sure that your underglaze is
destined for bad things, go ahead and include
tests of the proposed replacement underglaze in
the same test batches.
Sure, it's extra work, but isn't it better to know
while you can still make changes?
A fireplace may not be foodware, but it it still
vulnerable to accidental damage, and underfired
stoneware is even more fragile than earthenware.
Underfiring should be a last resort only.
I have a high confidence that overpainting with
more stable underglazes will give the results
you want. But test to find out!
-Snail
Kim Hohlmayer on tue 22 apr 08
Hi, Cathy,
I know next to nothing about tile production from my work as a potter, BUT I put new tile around a fireplace about ten years back. Your tiles should be fine fired below maturity except for the fact that they may not stand up to wear and tear as well as a higher fired tile.
Wood ash can be very caustic and if it mixes with water (a spill, when you scrub the tiles...)
it could possibly etch the glaze surface. Also, if you drop something heavy the tile would be more likely to crack or break. I speak from painful experience on that last point. Don't take me as the final expert remark on the subject. Others have a better chemical and physics background than I. However, I hope this helps a little.
Cathy Elliot wrote:
I am in the process of making some tiles for the hearth of my fireplace. I made the tiles by rolling
them out with my bailey mini slab roller. I have quite a few of them. I have decorated them with
Amaco velvet underglazes, and bisque fired them to cone 06. Now for the problem: today I was on
the web, and discovered a wonderful site, at http://www.brackers.com/product_info/amg_v_series.cfm
It is most unfortunate that I had not discovered this site before I painted my tiles!!! I say this,
because I got information from this site that was not available from anywhere else! One of the
underglazes, Terra Cotta, to be exact, apparently totally changes color when fired to Cone 5, and
covered with a transparent gloss glaze---which is exactly what I had planned to do! So now, I am
in a real mess. I have a lot of tiles. Most of them will be okay, fired to the maturity of my clay
body, which is cone 5--but a whole bunch are decorated with V-303 Terra Cotta, which they say
will fade away when glazed over and fired to Cone 5.
My question is: can I just put a glossy transparent glaze on these tiles, and glaze fire them to Cone
06? I know that is NOT the maturing temperature of the clay, but does it really matter if the tiles
are just going to be installed on a fireplace hearth? Of course, they do not need to be water
tight.... Also, should I glaze fire ALL the tiles to 06 instead of firing some to maturity, and others
to the lower temperature because of different shrinkage?
Sorry about the newbie question, but I have spent a lot of time on this project, and would like to
save it!
______________________________________________________________________________
Clayart members may send postings to: clayart@lsv.ceramics.org
You may look at the archives for the list, post messages, change your
subscription settings or unsubscribe/leave the list here: http://www.acers.org/cic/clayart/
Moderator of the list is Mel Jacobson who may be reached at melpots2@visi.com
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