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Terra sig density


Yvanox

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Hi everybody,

I made my two first batch of terra sig, one red and one white. I followed the Kari Raddash instructions from Clayflicks videos. I have two nice product to work with but before using them, I have to verify the density... I learn from another great potter that the target is around 114 gr for 100 ml to get the good density. So, I weithed my sigs with a measuring cylinder and a precise scale and one is 102 gr/100 ml and the other one 120 gr/100 ml. !

is that verry bad? I mean, I can use them like that? It mean that that did something wrong? Solutions?

tks ;)

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Vince Pitelka has very complete discussion of making, storing, etc. terra sigllata. 
 see  the sections on "Concentrating the Thin Sig by Evaporation" ,
"Accelerating Concentration of the Thin Sig by Heat,"
 "Determining the Specific Gravity for Application,"
"When and How to Apply the Terra Sig"
 
LT
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yes. add water. then you may have to adjust again..then boil it. it goes back and forth. The quick terra sig that I learned in Italy, does not rely on SG. This video 3 below is from my dvd. The bottle in the video is .591 ml and I added 125 grams.  The edited script says 750ml.  Its easier to use a liter bottle and 200 grams. see the recipe here. https://www.marciaselsorstudio.com/how-to-make-terra-sigillatta.html  Here is more detail. http://www.lameridiana.fi.it/pottery_clay_papers.htm  There are many ways to make and use terra sig. This is a good one immediately below for earthenware , but it is not good for my use in saggar firing. 

 

 

 

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Wow, tks Marcia you are so generous!

We finally come to the big question ... I have consult a lot of videos and recipes on the web and I am still confused! How come some arrive at very good results without too much precision and with little waiting times while others have a precise technique worthy of a laboratory with times that goes as far as 72 hours with specific gravity mesures?

Is there a kind of mysticism around Terra sigillata? Extra-precise not necessary chemistry?

Tks again folks for your generosity!

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2 hours ago, Yvanox said:

Wow, tks Marcia you are so generous!

We finally come to the big question ... I have consult a lot of videos and recipes on the web and I am still confused! How come some arrive at very good results without too much precision and with little waiting times while others have a precise technique worthy of a laboratory with times that goes as far as 72 hours with specific gravity mesures?

Is there a kind of mysticism around Terra sigillata? Extra-precise not necessary chemistry?

Tks again folks for your generosity!

Terra Sig was from the Greeks and Romans. I learned from the Romans.

except for the plastic bottle.

 

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55 minutes ago, oldlady said:

:Pmarcia, do not tell your age like that!!!!

My friend, Rosana Antonella just had an article about her terra sig work in PMI written by my other friend Claudia who manages the school program at La Meridiana. Rosana is from Rome...hence Roman!

Marcia

 

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BIG Question:

Is there a kind of mysticism around Terra sigillata? Extra-precise not necessary chemistry?

I think it depends on how you plan to use it, to find which way works best. The boiled terra sig above is leaving visible brush strokes on my work when I am focusing on surface patterns from the saggar firing. The fast terra sig that I learned in Italy, does not do that. Both are made with the same clay. My fast terra sig is thinner than the boiled type at 1.15 SG. I have been making Terra sig for several decades using various methods including ball milling for 24 hours. The fast terra sig works for how I use it.

Does this answer your question? 

Marcia

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Marcia: Yes, your answer illuminates my understanding! The text from Lamaridiana too! Tks for that!

I just fired test tiles with my white terra sig at 1.22 and my red terra sig  at 1.02. Everything seems OK, no peeling , seems to cover well, beautiful finish, beautiful colors.
So specific gravity is not such a big problem for me, I think ...

Also, I observed that oxides mix better with terra sig than Masson stains. Does anyone have a solution for that?

Thank you so much again!

test_tiles.jpg

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A former instructor of mine, Greg Payce works extensively with terra sig that he colours with both oxides and some stains. His advice was to add the Mason stains after the sig was decanted. The particles of stain are heavier than most oxides and they do settle out, but if you try and break them down in a ball mill, you will alter the fired colours, and not usually for the better.  He just worked with small batches and stirred frequently as he used it.

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  • 3 weeks later...

Fascinated by terra sig!  Have made and applied some with good result but now am ready for the next step and I realize that I do not see any instruction regarding firing.   I think I understand that the terra sig is an alternative to glaze so that it is now ready to fire with nothing more added.    Correct?  Do I fire to bisque temp (cone 06) or to final temp (cone 6)?

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1 minute ago, Yvanox said:

It is fascinating, for sure!

I am firing at 03 and the terra sig is beautiful, verry good results!

Don't know for other firing...

Well, I guess we are about to find out.  I have 4 pieces cooling right now.  They are (were?) high fire clay (Standard 306) covered with terra sig (with added oxides for color) and fired to Cone 6.  

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On 4/9/2018 at 4:52 PM, Yvanox said:

i am curious to know the results...

Well ... they are beautiful, but rough textured.  The oxides look great but look like they lack a coat of smooth glaze. 

What I dont understand is how a terra sig piece gets "finished out".   Do you just bisque it and then it is finished or do you glaze and fire again?  If there is no 2nd firing then its not particularly useful is it?   I would like to find a way to maintain that beautiful texture and shine that you get after app;lying and polishing  the terra sig, but also to have a durable piece of stoneware.  Ideas?

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I need advice about terra sig.  What do you do (or what CAN you do) AFTER applying and polishing the piece with the terra sig?   Are they bisque fired only?  Can they be glazed and fired to cone 6?  How do you maintain the beautiful texture and sheen that the raw terra sig piece has but still get a functional piece of stoneware?

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I just posted some recent work I have in a show plus a piece on the poster..pot on far right. The last obvara pot, the tiles, the 2 marble white pieces all have terra sig on them.I use ball clay so it is not going to vitrify at ^06. The shine is somewhat lost but it still absorbs fumes which is what I am doing. I polish the saggar and the foil saggar with wax. the obvara is natural finish.

 

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On 4/18/2018 at 9:09 AM, Rick Wise said:

I need advice about terra sig.  What do you do (or what CAN you do) AFTER applying and polishing the piece with the terra sig?   Are they bisque fired only?  Can they be glazed and fired to cone 6?  How do you maintain the beautiful texture and sheen that the raw terra sig piece has but still get a functional piece of stoneware?

your pieces look great. Terra sig was originally used to seal lowlier earthenware. Many artists today use it for a sculptural finish at higher temperatures. If you put a glaze on top of it, I would wonder why use it in the first place?

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