Adding Stains To Terra Sigililata

[Alondene]

Hi ,

I'm have decovered developed a passion for terra sigililate and so far have successfully managed to get great results with the recipes. My issue though is in adding the stains. In the UK, Mason stains aren't so easy to get and I've been using Nano stains( great colours) however the stains sink and settled to quite a hard substances at the bottom. Did sieve them but don't have a drum thingy to turn the recipe in. I can revive each time but wondered if added a little bentonite would help of if anything else might help. My sig recipe is from Pete Pernell , OM4 ball clay, Sodium silicate and water. It's a great consistency and everything else seems fine.

 

Any suggestions or advice would be really appreciated- I've got a set of bone dry pots, I'm dying to decorate. Thank you

[PeterH]

In the UK, Mason stains aren't so easy to get

 

Scarva seem to offer them.

http://www.scarva.com/en/gb/Mason-Stains/c-43.aspx

 

[Alondene]

Mason stains - Thank you both, will look into Scarva.

 

 

Understanding its to do with the particles is good to know, leads me in a new direction. So much to get your head round and try, but so moorish.

 

Thank you

[Kellykopp]

I have been dabbling with Terra Sig, and have had success with the oxides, and have recently tried the Mason stains ( just to see what would happen ), with the same settling problem you are having.....I was wondering about the Bentonite myself, but when I apply the sig with the stains included I just continually stirred the mixture.  I still have yet to fire the pieces I applied the Sig/stains to, but I can tell you that when you go to polish the piece after the sig application it doesn't shine up as readily or as well as the plain sig without the stain in it, which as Tyler mentioned that sigs are the finest of the fine particles, which gives you the shine when you polish (lay the platelets flat and it reflects the light)  I have been bisque firing to ^014 and then barrel firing the pieces.  These pieces are not functional in any way, as the oxides/stains are not stable.  I have had a blast making/using the sigs; it is like magic when you polish the piece and that luster develops under your fingertips.  Good luck and let me know how they turn out.  Take a peek at my work in my gallery it will show you some of the colors I have been getting.  Have fun experimenting, and keep good notes of your tests.

[PeterH]

A word of warning, inspired by a post of Tyler's that seems to have gone.

 

From: http://claystore.alfred.edu/rawmats/presentations/Raw%20Mats/Class-11%20%28slips%20and%20engobes%29.pdf

 

Cautionary note:

Many metal oxides are not food safe in slips (because slips lack the glassy structure found in glazes)
 
If its not safe in the raw state, chances are it won’t be safe in a fired slip either

 

The low-fire nature of terra-sig only emphasises the message.

 

PS A beautiful example of terra-sig used in non-functional smoke-resist raku.

I believe the terra-sig has added iron oxide, and was milled.

http://www.duncanrossceramics.co.uk/details.php?image_id=2&cat=2

 

For what it's worth you can buy very fine (~1μm) iron oxide as artists pigment -- at a price.

http://www.kremer-pigmente.com/en/pigments/iron-oxide-red--micronized-48289.html

Look for local distributor and/or check payment options. Years back I bought something

from them, and had to pay via my bank (with currency currency fee).
 

[High Bridge Pottery]

Is the sodium silicate making this problem worse? If I understand it right it makes particles repel each other. I would think with the fine clay it would suspend the oxides better but does the silicate stop this allowing the hard panning. 

 

Never used sig so not sure on how you are meant to apply it and if the silicate is needed.

[Dick White]

Joel, the sodium silicate (or soda ash or Darvan) is necessary to make the terra sig. The deflocculation effect causes the ball clay particles to repel each other and start sinking. The largest particles of clay sink faster and the finest particles sink slower. Using that differential in sink-rates, in a short while the bottom of the jar will be gooey sludge while the finest particles are still floating in the top 2/3 of the jar. Decant those off into a separate container before they too sink, and now you have terra sig. I've never tried re-flocculating the finished siggy to keep it suspended in later use; an interesting idea I will try. Thanks for making me think about it.

But back to the original question, it is also my experience that stains have a larger particle size that contradicts the polish of the siggy. Some oxides aren't much better. You might try mixing a dab of commercial underglaze into a small amount of siggy and see if that gives you some color without affecting the surface shine.

[Patat]

This is just a guess, but might be worth trying. Sodium silicate is a deflocculant ie stops particles from sticking together. Traditionally when you make terra sig, you use this feature to force large heavy particles  settle out and remove them. If I remember OM4 is so fine, you don't need to do the separation step (correct me if I'm wrong there), so don't add Sodium silicate to start with. ie just use an OM4 slip with colourants.

If you still do the separation stage add acid to neutralise the sodium silicate. Vinegar works good. I've only used the vinegar trick to process hand dug clay, so not too sure how well it will work with sig. 

The other thing you could try is decreasing the water content of your final sig. This increases the effective density of your sig so that it can suspend larger particles.

Let us know how you made out. I'm curious.

[Callie Beller Diesel]

Everyone go look at this guy first: http://www.artoronto.ca/?p=6908

 

Ok, now that you're back.

Greg Payce was the Ceramics Department Head when I was at ACAD, and taught my first glaze chem and throwing classes. At the time, he was working heavily in earthenware with terra sig. He did use Mason stains to get all those brightly coloured stripes. He would make up the sig, and because of the particle size already noted, add the stains after. You do indeed have to keep stirring this sig while applying.

One thing he did teach us was that if you ball mill Mason stains (for those that might have access to a ball mill, or even a lapidary polisher) it alters their colour. I would suspect this is particularly true of any encapsulated stains.

[PeterH]

From a lost digitalfire entry captured by clayart at:

http://www.potters.org/subject49916.htm

 

Vince Pitelka

I always like to work with pure clay terra sigs, because they give the best
shine. It is of course natural that others will want more color, but unless you
can ball-mill the mixture the shine will be reduced. At U-Mass we experimented
with both oxides and mason stains and got good results by ball-milling the
thickened evaporated terra sig and colorants for a day or so. I have used both
oxides and mason stains without ball-milling, and the shine is reduced
slightly, but the results are still satisfactory. [My emphasis.]

 

[Alondene]

This terra sig stuff is just so interesting and I love a challenge, so the advice and info is just brilliant. I added the stains after making the sig and have tried an amayco underglaze in one of them and that' one hasn't settled. It's a pricy option though. I've just done some tests samples with the stains and tried burnishing, doing multiple layers and over laying, firing to 990. Even through the stains need a really good mix, the samples were great, almost cream and nearly all of them retained the burnished sections, so I'm really chuffed. I'm now wondering if I sieve finer, might this will make a difference by just retaining the smaller particles?. Going to give it a go.

 

Also this idea I'd ball milling, what is that? I have something like this I used for washing stones and polishing jewellery, like a tumbler with hundred of shots inside. Is this the same thing they mean or am I on the wrong train again.

 

Thank you everyone, it's good to get ideas and advice, makes experimenting much more fun than fumbling along on your own.

[Alondene]

I'd like to try oxides at some point but need food safe at this stage, also I'm a bit cautious of them, even though I love the results they achieve.

[bciskepottery]

You can use a rock tumbler for ball milling.  Same principles.

 

One caution about ball milling encapsulated stains.  In an earlier thread (see link below) we learned that ball milling can break down encapsulated stains . . . which means if your stain has cadmium or vanadium, etc, the colorant may not longer be "food safe".

 

http://community.ceramicartsdaily.org/topic/3725-encapsulated-cadmium/

[High Bridge Pottery]

There is really no difference between raw colouring oxides and purchased colours besides that they have different mixes of extra stuff. Colours are all achieved in the same way so the hazards still apply to their products.

 

This is the most simple ball mill I have seen, always wanted to make one but it has not happened yet.

 

 

[Dick White]

... and have tried an amayco underglaze in one of them and that' one hasn't settled. It's a pricy option though.

Do not add the colorants of whatever source until after you have made the siggy. If you put them in the raw batch, they will settle down into the sludge that will be thrown away. That's what makes it pricey - it's all thrown away. Take a quarter cup of the finished siggy and stir in a glob of underglaze until it is thoroughly mixed. Use that on a small test piece to see how it takes.

[Alondene]

Re:Dick White( not sure how to Copy a post and add it in to respond- new to this)

Do not add the colorants of whatever source until after you have made the siggy. If you put them in the raw batch, they will settle down into the sludge that will be thrown away. That's what makes it pricey - it's all thrown away. Take a quarter cup of the finished siggy and stir in a glob of underglaze until it is thoroughly mixed. Use that on a small test piece to see how it takes.

 

 

Hi,

I haven't any any stains till after I have made the sig, only when I'm developing a batch of coloured sig. What I meant to relay was that the amount of underglaze required compared to using the raw stain is much greater to get the same level of colour intensity, so it's costing more. Although so far, it seems that there's very little settling of the underglaze in the mix- which would I guess indicate that the particles in the underglaze are either very fine or there's a component in the underglaze mix that's helping to keep it suspended

 

Ummm? Makes me wonder if a same amount if bentonite might help? Another test to try, I think.

 

One thing that's definitely come out of the testing , is that having the right thickness of the sig is really important to how it burnishes or applies with the stains included. I've been using Jeremy Randalls method with specific gravity and it's worked well. I also saw another video where sig was simmered to thicken it, once it had thickened and cooled, it achieved a shine without burnishing - that looked really interesting- I'd add the link if I could work it out.

[Alondene]

Thank you for the ball milling vid and all the info, will definitely look into it all and see how things work out.

 

 

Here's the link for simmering sig:

 

 

 

Jeremy Randalls specific gravity:

 

 

[Alondene]

Sorry posted the wrong one - this is the simmering sig

 

 

[dee3]

Hi all my name is Deirdre and I am in the west of Ireland. I have been experimenting with coloured sigs aswell with both mason(scarva pottery supplies) and nano colours. I find with the stains you have to constantly stir the sig and not the same same shine as the plain white or red sig. I have been looking into washes to apply after bisque to add shine, I am yet to fire tests of these. Washes made of soda ash and borax , I am going to try these out in my next firing in a couple of weeks.

[Kellykopp]

Let us know how the washes work out Dierdre. How do you fire the work?

[rakukuku]

Hi, I've used a lot of colored terra sig in naked raku pieces.  I found using mason stains to be problematic because even with ball milling, they still settled out.  What worked better was colorant oxides like iron, rutile, chrome, copper etc.  I looked in Vince Patella's book and there is a section about how much oxide to use for various colors. Iron can go from deep red to pink. Anyway I mixed up a big batch of plain and then added various amounts of the oxides. They can get moldy over time so I rescreen them once in awhile.  Someone told me that terra sig should always be kept in glass jars as they can react with plastic. rakuku

[Kellykopp]

Rakuku I've never heard about the glass jar vs. plastic container for sigs.  Interesting.  I have had them in plastic containers with no problems so far, but it has only been a few months, and I go through it pretty quickly.  The only thing I know for sure from reading Vince's work on sigs is that if you dry them all the way out they can be stored forever.  Haven't had a mold problem yet, either, but I don't think that would be a problem, would it?  Clay can get mold on it, and though I wouldn't want to breathe it or have it start growing in the studio; once you knead the clay it works and fires ok.  I even made the sig in plastic 5 gallon buckets.  My best success has been with the oxides as well.  The stains, while they do give color, tend to be gritty, settle, and don't polish up as well.  

[dee3]

I fire in a gas downdraft kiln, I bisque to 06. I will let you know how my tests go, just waiting on stuff to dry.

[rakukuku]

The advice about using glass containers for terra sig came from an alternative raku workshop by Eduardo Lazo. Not sure how it would react other than plastics can break down over time.  I don't like glass in the studio but use glass canning jars for this purpose.  And the mold I get is sort of green looking moss stuff. Glass jars do let in light. But it doesn't seem to hurt anything.

 

The Vince Patelka oxide combinations are I think in his section on colored slips which obviously also do the same in terra sig because it is a slip. I like combining streaks of different colors and then doing naked raku on pieces.    rakuku

[Alondene]

Hi all my name is Deirdre and I am in the west of Ireland. I have been experimenting with coloured sigs aswell with both mason(scarva pottery supplies) and nano colours. I find with the stains you have to constantly stir the sig and not the same same shine as the plain white or red sig. I have been looking into washes to apply after bisque to add shine, I am yet to fire tests of these. Washes made of soda ash and borax , I am going to try these out in my next firing in a couple of weeks.

 

 

Hi Deirdre, I'd love to hear how your washes on bisque come out and good to know that the settling is an issue with most stains. May first batch of sig was a little to watery but the second was good and that's made some difference.

 

On the latter post about plastic versa glass, I can't see a difference. Just out of necessity I have a mix of both and still notice the same settling in both. It great to hear others experiences of what does and doesn't work, I've got a large sketch /note book to record everything and use a circular disks with a texture pattern in the middle to see how glaze sits or moves. They have a slight curve and I make a whole and can hang or string them / mark them together in batches, that way I find I can return to them later and remember what I did.

 

Do let us know how the borax works, I'm exciting to try this as I believe it's supposed to add a pop to the surface.