BBarus on tue 23 oct 01
I am being introduced to such wonderful and fascinating subjects - and
engobe is one. I remember them from long ago but back then I wasn't
impressed by how my teacher was using them - (her designs made my teeth
itch). I have since seen some newer work and I think that the use of an
engobe may simplify one of my tile needs. Here are the Questions: Can an
engobe be easily pushed through a syringe? Will it stick to soft fired
porcelain? How thick does it need to be not to pop off the porcelain? Can
it then be fired to at least Cone 5? Will it then take a translucent
glaze? 4000 stars to go.
Thanx
Barb
Snail Scott on wed 24 oct 01
Barb-
Engobe isn't really one thing, any more than a
glaze is. It's a whole range of things, covering
most of the range between plain 'ol slips and
actual glazes. You could think of most engobes as
slips with additives and modifiers.
At 10:36 PM 10/23/01 -0400, Barb wrote:
>Can an
>engobe be easily pushed through a syringe?
The consistency is up to you. Just mix in enough
water to make it runny enough. Some folks like to
add glycerin or polyglycol to get a smooth, satiny
consistency, but it's not really necessary.
>Will it stick to soft fired
>porcelain?
You will need to select an engobe recipe which
has a low 'green' shrinkage. This will most likely
mean a recipe with only a little clay, or one in
which the clay has been calcined. Some recipes
will be labelled 'for greenware', for leather-hard',
or 'for bisque'. Try to find a 'for bisque' recipe.
A few experiments may be necessary to find one
which fits your clay body; try several different
recipes.
>How thick does it need to be not to pop
>off the porcelain?
The thicker it gets, the more likely it is to pop
off, not less. See above for minimizing shrinkage;
that's the big reason things pop off. The other
is when the engobe isn't vitrified enough, it won't
melt enough to stick. To avoid this, pick a recipe
that's designed for your specific temperature range.
>Can
>it then be fired to at least Cone 5?
If it is a ^5 recipe, yes. Engobes are less fussy
about maturation temperature than glazes are, so you
may find recipes labelled ^1-8, or something similarly
broad. Try to find one that's not too broad, or one
where ^5 is close to the top of its suggested range.
>Will it then take a translucent
>glaze?
Most will. Remember that some glazes can change the
appearance of the colors underneath; you may need
to do a few tests to find the best combination of
engobe and glaze.
I don't generally apply them to bisque, so my recipes
won't really help you, but Chappell's 'Potter's Complete
Book of Clay and Glazes' has engobe recipes, as do
others.
-Snail
Timakia@AOL.COM on fri 26 oct 01
Barb, you will possibly find many different answers to what an englobe is. To
my knowledge and experience an englobe is something between a slip and a
glaze. When you fire it to a bisque temperature, it will start showing
caracteristic of a glaze. At a higher temperature it will look like an
immature glaze. For that reason it will need a glaze on top of it to bring
out the qualities.
A regular slip will act like a clay layer on top of clay.
Now; you can mix a slip from your clay body, by simply adding extra water to
end with a creamy consistency, add colorants or oxides and paint that on your
work at a wet, cheese or leatherhard stage. Some clays will allow you to put
it on at leatherhard stage but will flake off during the bisque firing. So
you will have to test that with your own clay body.
The other way to make a slip will be to mix up some ingredients that will
bring you closer to an englobe, but do the same as a slip and will allow you
to use it on different clay bodies.
Here are some recipes that I used over the years. I got them at a workshop
years ago and cannot remember who was the potter.
This is a slip to use on wet to (soft) leatherhard clay.
Kaolin 55
Ball clay 15
Whiting 10
Potash Feldspar 10
Silica 15
Add colorants or oxides.
I know it counts up to 105, but it worked al the years this way, so I had no
reason to adjust it. In the US I adjusted the recipe to EPK and Kentucky ball
clay. In South Africa I used Kg 1 and B13.
The following recipe can be used on bone dry to bisque pieces.
Silica 20
Kaolin 6
Ball clay 6 (as white as you can get)
Potash Feldspar 10
Whiting 3
Nephline Sygnite 12
Fritt 1886(in South Africa) or 3110 (USA) 23
Zircon Opacifier 10
CMC 5
Add colorants or oxides.
Again this recipe does not count to 100, but it worked for me. You will find
that you can not brush it on easily, it is too "dry" Wet your brush with lots
of this mixture and do not worry if it look uneven on your work. Just make
sure of an even thickness when you apply it on your work. Use it in a siringe
and do slip trailing with it, or pour it on or in a pot. When clear glaze is
fired on top of it, it smoothes out beautifully. O yes I almost forgot, It
settles down fairly quickly to the bottom, but it stirs up with not too much
effort (I use a fork), so I never tried to use a deffloculant. I cannot tell
you what will happen when you add one.
Please remember to make tests for yourself before mixing a big batch so that
you can make sure that you will be happy with the end results.
I do believe someone posted a different recipe a while ago that might do the
same. You will find that in the archieves.
Hope this will help you on your road to experimenting with success.
Regards.
Antoinette.
http://hometown.aol.com/timakia
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