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Burnishing Terra Sig


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So I messed up my first try at Terra Sig...didn't burnish just after applying. (Don't know what I was thinking).  Reading in Sumi vonDassow's Low-firing and Burnishing book she describes in great detail about wetting the pot,and using oil, but not in conjunction with terra sig.  For that, she only describes burnishing between coats or just after applying. I have tried polishing now, but the terra sig just seems to be rubbing off slightly.  No sheen.   Can I use either water or oil at this point or is it too late to do anything?

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@flowerdry, It is a little tough to diagnose something like this...there are a number of variables involved.  If your piece is still leather hard, try applying a new, thin layer of Terra Sig on a small area, say 4" x 4", let it set for a minute, and then polish that area to see if you can achieve the sheen you are looking for.  I use those thin, disposable grocery bags for rubbing/polishing (basically stretching a small section tightly over a finger).  Timing is the key for great Terra Sig...if you try to polish it when it is too wet it  smears, if you wait until it is too dry it is tough to impossible to get good results.  Multiple thin layers, polishing between layers, gives me good results...and I rarely try to do an entire surface, always small sections.

 

I am an advocate of Vince Pitelka's ultra fine Terra Sig process...and I know that there are simpler processes around.   Here is information from Vince that includes tips/instructions for applying/polishing: Terra Sigilatta

 

My last tip...don't give up. Keep experimenting, that's half the fun of learning how this works!

 

-Paul

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Thanks, Paul.  For me, the experimenting is way more than half the fun!

 

Yes,it's the timing that's the problem here.  The pot and terr sig layers are completely dry and now I want to polish.  I'm afraid that if I try to apply more terra sig and polish it will all crack off.  Neither Vince nor Sumi mentioned what might happen in such a case, I guess because folks generally remember to polish while it's still slightly moist.  I'll probably end up just reapplying and see what happens.

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What are you trying to do?  Whats the end result you want?

If for example trying to get a smooth burnished surface,  there may not be a need for terr sig.

If for example trying to get a pigmented smooth suface, there may be a need for ter sig.

If the terr sig is flaking off, it might mean that the sig and clay body is shrinking at different rates...so add

   a little clay to the sig to slow down the rate.

If a solid black surface is what is needed, then no terr sig is needed.

 

Make some test tiles and use different oils, grease, and butter to see what fits your needs.

Now if test tiles are boring, then make round test tiles with one or two holes in the top so you can make a necklace

out of the test tiles and wear them!!  Oh, coating and polishing the test tiles with Turtle Wax or something to that  

effect will bring out the shine after they're fired.

      There is a knack to burnishing I found out long ago.  I ws burnishing test tiles when someone came in and asked

to try it.  Whats the harm? right?  I handed it over to them and they burnished it away!!!  They gave it back and

it was burnished again...and they wanted to try it again.  And they burnished off the surface again.  They didn't

get it back... Up until then, I thought anyone with a pulse could burnish.  Have fun, try different methods.

 

Good luck,

Alabama

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i use terra sig a lot. just brush on two coats (don't polish in between) and then as soon as it is dry to the touch, polish gently with a micro fiber cloth or old t shirt.  its a light buffing, to me its not really burnishing.  if you burnish, you don't need tera sig.  i use colored tera sig alot and then do naked raku.  colored tera sig recipes are in the vince patelka book handbook for the studio potter.  rakuku

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I don't use terrra sig much but when I do I apply it to a realy dry pot, so I think you could get ok results reapplying another coat or two and then burnishing if you must. the terra sig will give you a sheen without the burnishing,.onlyenemy after that is your kiln temp.

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First of all, thanks to all who took the time to reply.  I appreciate it so much!  Secondly, I think I need to brush up on my communication skills since it was apparently not very clear what I was asking.

This was a case of a single pot where I guess I was "asleep at the wheel" when I applied the terra sig because I forgot to polish.  So now I have an answer to that particular question....if you don't polish right then, it doesn't work to come back the next day and try to polish when everything is bone dry.  

After some more reading, I think it really is incorrect to use the term burnishing with terra sig as I did.  Burnishing really seems to apply to the "naked" clay only.  So now I've got that straight.  (It's a journey...)

I went ahead and applied a single thin coat of terra sig step wise up the pot and polished as I went.  That seemed to work.  The pot now has a lovely sheen and is ready for bisque.  I gather that if the terra sig is applied too thickly it can crack or flake off, so I quess I'll just have to see how it does in bisque fire.  But then...the "it ain't over til it's over" mantra applies to all our pots, doesn't it.

Thanks again and I'll let you know if it doesn't work out!

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Hey,

I forgot to say that all my burnishing tests were on leather hard examples, and the clay was from local

river banks...it seemed better than stoneware clay which streaked.

Once I wedged in a couple of tablespoons of vegetable oil in the clay to see if I could by-pass rubbing oil

on the vessel itself...it worked.  But I only tried it once.

The different items I've burnished with have been pecans, hardwood handles, spoons (didn't like), and

smooth stones (Knox chert).

 

I'd take a sheet of paper and systematically write types of burnishing:

1. burnishing in one direction,

2.  burnishing in two directions (seems to gloss better)

3.        "     with pecans

4.        "     with spoons....etc. 

I tried everything once and made notes both written and mental.

 

When the Head of the Archaeology Dept. wasn't in, I used his coffee pot and filters to make Terra sigellata.

That did explain the wood ashes.

See ya,

Alabama

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If the sig flakes off, it's too thick. It should be quite watery.

 

If the pot is too wet, it's harder to get a good shine if you're burnishing with something hard like a stone or a spoon. In that case just polish it with something soft. You can burnish bone dry pots, just put on the sig and go at it. Just be careful you don't push too hard and crack the pot. I knew a guy who did all his sig burnishing on bone dry pots, using lard as a lubricant. Beautiful shine!

 

Don't bisque too hot or you'll lose a lot of the shine.

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  • 4 weeks later...

>>>>>Alabama what do yo say when he offers to share a coffee with you??<<<<<

 

Your won't believe this, but as a student spending countless hours in the arch. lab. I brought my own

coffee pot, the perculator kind.  I found it to taste better and less bitter.  So I couldn't use mine because

there was no grounds basket. :>)

In the lab, there were hundreds of sherds from around the world to look at or study.  I found out quick

the difference between burnished pottery of pre-historic Mississippian, historic Creek, and modern San Ildefonso.

I was able to study one of Maria Martinez' 1938 era black on black vessel.

 

So, Flowerdry there are 2 kinds of polished pottery.  One which represents each sequence ie. oxydation and reduction.

If you are planning a polished pot for reduction, then there is not a reason to apply terra sig. 

If you are planning to make a red pot from a tan clay body, then you'll need to apply a pigment and burnish

the pigment into the surface.  I think the red you want will be a mixture of powdered red iron oxide(hematite)

and water...the red iron oxide doesn't change much during the firing.  If your wanting a red orange color then

you'll want to use powdered yellow iron oxide (limonite).  If you fire the yellow iron oxide, then the wood

needs to be known dry and not, I think the wood is dry.  It'll be the difference between a red orange and a brown.

Its been a long time ago, but if memory serves me, the heat from the wood has to sinter the limonite by driving

out molecules of moisture, and once I found this out during a demonstration that damp wood won't do it.

Black pottery is made by covering a pot with organic material right after its been fired.  The size of the material

matters... If you use large leaves like those on a White Oak tree, you'll have about 4 to 8 seconds before the blaze

will be so hot it can't be smothered with sand.   Leaves from the Pin Oak or the Live Oak is better, because the

small leaves gives you more time to cover it with sand or loose dirt.  Powdered manure is good, because it

mostly smolders.  The downside of powdered manure, is that there isn't much substance/structure so you'll

either need alot of manure or some sides in the way of logs or bricks along the firing area.  And just as the

wood has to be dry, so does the reduction material, if you want the glossy black pottery and not glossy

mottled grey and black surfaces.  That covers burnished solid pigments.

     If you're after the "black on black" pottery, then burnish the whole pot, then paint on white clay(don't burnish)

and fire it, covering it with organic material.  If you're after the "red on red" then burnish on the red iron oxide,

paint the designs with white clay (don't burnish) and fire and let the wood and ash burn down.

    If you look at Polychrome pottery, you can see that the tan area is actually the clay body, the red is hematite,

and the orange is limonite, and the black could be either black iron oxide or a mixture of mountain bee balm

juice from the year before...Don't ask!   I always thought black lines could be made if you could mimic a mixture

of honey and flour,hoping to make a "paint" that would leave an ash and under the ash would be the

carbon traces of the mixture in question.  I did try painting pottery with a sugar solution, since it was thought

that the oxidized pottery with the black lines were made from some type of carbohydrate which sugar is.  It left

a faint image on the surface, ..I didn't pursue it any further...

Hope this helps.  I got alot of this info from a Mercedes car magazine where they did an article on modern

South West pottery.  The article showed the pottery before and after it was fired, which made it obvious

what steps were taken.  Oh, I did all the extracting of terra sig from different clays and when fired, they all

turned brown in oxidation.  Thats why I suggest the iron oxides for oxidation.

Alabama

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