=3D?iso-8859-1?B?VGlnIER1cHLp?=3D on mon 5 sep 11
Dear Mudbuds=3D2C
A few weeks ago I posted commentary about my cracking handles and asked for=
=3D
help. Many of you generous folks offered helpful suggestions=3D2C some of=
w=3D
hich I incorporated in my production. Ron Roy gave me some particularly he=
=3D
lpful advice=3D2C and I decided to do some experimentation. Here are the r=
es=3D
ults.
This is an extract of the email I sent to Ron=3D2C thanking him for his hel=
p.
I think I may have solved the problem of the cracking handles! And=3D2C =
=3D20
I may have isolated the cause=3D2C as well.
Thanks to your suggestions=3D2C I did a series of experiments. First=3D2C =
I =3D20
wedged some apple cider vinegar into about ten pounds of porcelain =3D20
clay by slicing it into 1/4" thick plates=3D2C spraying the plates with =3D=
20
vinegar=3D2C then reassembling the pug and wedging it thoroughly. I =3D20
then made a dozen mug barrels and extruded my handles normally=3D2C =3D20
shaping them on a mold to make them oblong. I made four handles on =3D20
the mold sprayed with WD-40=3D2C four on the mold dusted with corn =3D20
starch=3D2C and four on the mold sprayed with vegetable cooking oil. =3D20
The purpose of coating the mold is to facilitate removal of the =3D20
shaped handles=3D2C which I then cut to a "D" shape and attach.
I attached all the handles with a slip made from porcelain throwing =3D20
slip and vinegar=3D2C in the usual fashion. The results were =3D20
illuminating!
The four made with WD-40 ALL cracked. None of the other eight =3D20
handles cracked at all. It would appear that the WD-40 is the =3D20
culprit. Since WD-40 is a "water displacement" formula=3D2C not an =3D20
actual lubricant=3D2C it possibly affected the clay=3D2C weakening it at th=
e =3D20
places where the WD-40 came in contact with it. This caused an =3D20
imbalance in the water content of the clay=3D2C which caused it to dry =3D2=
0
unevenly=3D2C creating the cracks. That's my theory=3D2C anyway.
I am waiting for all the mugs to mature to bone dry before bisque =3D20
firing them=3D2C which is the final test for cracking faults.
(NOTE: as of this posting the mugs are dry and in bisque fire=3D2C
with NO cracking at all.)
By the way=3D2C I found that the clay treated with vinegar also throws =3D2=
0
more smoothly and seems to handle better than the untreated clay.
Many thanks again to all the regulars at the Ram's Head Pub!
Tig Dupre
in Port Orchard=3D2C WA
=3D
Lee on mon 5 sep 11
On Mon, Sep 5, 2011 at 9:17 AM, Tig Dupr=3DE9 wrote:
>
> places where the WD-40 came in contact with it. =3DA0This caused an
> imbalance in the water content of the clay, which caused it to dry
> unevenly, creating the cracks. =3DA0That's my theory, anyway.
I =3DA0wonder what effect glycerin would have? Since being unable to
get my hands on Cornhusker's lotion, I've been making my own out of
food grade glycerin and rosewater from the middle eastern grocery.
I've seen it recommended, to mix majolica oxides with glycerin.
--
=3DA0Lee Love in Minneapolis
http://mingeisota.blogspot.com/
=3DA0"Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=3D9=
7that is, =3D
"The
land of eternal youth is behind the house, a beautiful land fluent
within itself." -- John O'Donohue
Steve Mills on tue 6 sep 11
As I have said many many times: Vinegar is amazing stuff, especially for pl=
a=3D
sticising Clay!!!=3D20
:-)
Steve M
Steve Mills
Bath
UK
www.mudslinger.me.uk
Sent from my Ipod touch
On 5 Sep 2011, at 15:17, Tig Dupr=3DC3=3DA9 wrote:
>=3D20
>=3D20
> A few weeks ago I posted commentary about my cracking handles and asked f=
o=3D
r help. =3D20
>=3D20
> By the way, I found that the clay treated with vinegar also throws =3D20
> more smoothly and seems to handle better than the untreated clay.
>=3D20
>=3D20
marci Boskie's Mama =3D^..^=3D on tue 6 sep 11
> Lee said:
>I =3DA0wonder what effect glycerin would have? Since being unable to
>get my hands on Cornhusker's lotion, I've been making my own out of
>food grade glycerin and rosewater from the middle eastern grocery.
> I've seen it recommended, to mix majolica oxides with glycerin.
Hi Lee,
Glycerin might help keeping the clay wetter ( I ve added it to
the spares from slip cast porcelain to make the clay a little less
short for building attachments ) but I dont think thats why its used
with majolica oxides. In chinapainting , we use glycerin as a
waterbased medium for the paint and I would imagine it serves a
similar purpose in majolica .
marci the chinapainter
Lee on tue 6 sep 11
On Tue, Sep 6, 2011 at 12:51 AM, marci Boskie's Mama =3D3D^..^=3D3D
wrote:
> Hi Lee,
> =3DA0 Glycerin might help keeping the clay wetter
I believe Tig uses oil i as a lubricant for extrusion. My question
is, could you use glycerin in spray form for the same thing. I have
no idea if it would eliminate or exacerbate the cracking problem, but
it would be worth testing.
Glycerin is the main ingredient in "personal" lubricants.
The nice thing about it, in Corn Huskers or my own homemade, is that
it is a good hand treatment for potters, that does not cause trouble
like grease or oil does when you are glazing.
--
=3DA0Lee Love in Minneapolis
http://mingeisota.blogspot.com/
=3DA0"Ta tIr na n-=3DF3g ar chul an tI=3D97tIr dlainn trina ch=3DE9ile"=3D9=
7that is, =3D
"The
land of eternal youth is behind the house, a beautiful land fluent
within itself." -- John O'Donohue
marci Boskie's Mama =3D^..^=3D on tue 6 sep 11
At 07:12 AM 9/6/2011, Lee wrote:
>On Tue, Sep 6, 2011 at 12:51 AM, marci Boskie's Mama =3D^..^=3D
> wrote:
>
> > Hi Lee,
> > Glycerin might help keeping the clay wetter
>
>I believe Tig uses oil i as a lubricant for extrusion. My question
>is, could you use glycerin in spray form for the same thing. I have
>no idea if it would eliminate or exacerbate the cracking problem, but
>it would be worth testing.
> It would be worth trying . Its hygroscopic so it pulls moisture
> out of the air so it might be useful where slower drying is needed
> . Like I said, mixing it in with porcelain casting sprues lets me
> make a workable , if not fabulous, clay for making add-ons for
> castings and y oure right, it doesnt affect the clay as far as
> glazing or any of that sort of thing . Its relatively cheap and
> easy to find.. so it would definitely be worth trying in the
> extruder... although it might create cracks from keeping too much
> moisture ( if the cracking problem she has was because the WD-40
> was pulling out the water ) .
marci
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