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Fertilizers For Pit Firing


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#1 Isculpt

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Posted 26 September 2013 - 09:18 PM

I'm wondering what component in fertilizer contributes color to a pit fired ceramic piece.  Some fertilizers are more expensive than others, so I'm thinking that if I knew which component created color in a pit firing, I could price shop fertilizers without running the risk of buying a cheap fertilizer that is missing the agent needed.  Lots of folks on the Forum have mentioned Miracle Grow, but it's relatively expensive.  I'm hoping to find a cheaper alternative....

Jayne



#2 jrgpots

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Posted 26 September 2013 - 11:43 PM

In another thread in the clay and glaze forum talking about saggar firing, copper nitrate, a root killer was mentioned to be less costly than Miracle Grow. Many nurseries will carry it in large bags.

#3 Isculpt

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Posted 27 September 2013 - 06:10 AM

thanks....it seems ironic that fertilizer and root killer would both offer something useful for pit fring!



#4 JLowes

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Posted 27 September 2013 - 12:30 PM

Copper sulfate is an active ingredient in root killers, it may be the only ingredient other than inert filler.

 

I am not sure that copper nitrate is what you want...quoted from an article "Cupric nitrate is a strong oxidizer which can cause burning and explosive if heated, rubbed or impacted with carbon powder, sulfur or other combustible materials"
 

John
 



#5 jrgpots

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Posted 27 September 2013 - 02:20 PM

Copper sulfate is an active ingredient in root killers, it may be the only ingredient other than inert filler.

 

I am not sure that copper nitrate is what you want...quoted from an article "Cupric nitrate is a strong oxidizer which can cause burning and explosive if heated, rubbed or impacted with carbon powder, sulfur or other combustible materials"
 

John
 

Thanks John for the correction.



#6 Bob Coyle

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Posted 27 September 2013 - 06:33 PM

There is no copper sulfate in plant fertilizers. they contain mixed phosphates, nitrates, and maybe some iron. If you want copper sulphate, then you should specify "root killer". This is almost pure copper sulphate crystals. This (and ferric chloride) is what most people use in pit fires or aluminum foil sagger fires.

#7 Isculpt

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Posted 29 September 2013 - 12:47 AM

Thanks, all. I had never heard of a dry root killer until I read these posts and Googled it.  I found copper sulfate crystals as well as powder, but I only found liquid versions of ferric chloride.  Surely you don't pour liquid ferric chloride on pottery?  Are either of these available at big box hardware stores - or only available online?

Jayne



#8 Bob Coyle

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Posted 29 September 2013 - 10:30 AM

Yes you do pour liquid ferric chloride on pottery, or brush it or dab it on with a sponge. It is corrosive stuff so you have to be careful. The root killer you can get at Home Depot or Lowes. The ferric chloride used to be sold by Radio Shack to make electronic PC boards, but I don't think they have it any more.

I make my own with muriatic acid and steel wool (Home Depot). Just put a pint of water in a quart jar and add half a pint of muriatic acid SLOWLY then drop a couple of pads of steel wool in and let it sit. Keep throwing pads in till no more dissolve. the yellow liquid you get is ferric chloride.

I don't recommend you do this unless you have some understanding of the chemicals and wear gloves and safety glasses. There is lot's of info on the internet if you want to pursue it.

#9 JBaymore

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Posted 29 September 2013 - 10:30 AM

Jayne,

 

You can get ferric chloride solution (relatively locally in most places in the US) from Radio Shack....... it is used for etching printed citrcuit boards.

 

best,

 

....................john

 

EDIT:  Hummmm.... Bob says above they don't carry it anymore. Oops.. sorry.  Haven't bought it it a while.


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#10 PeterH

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Posted 29 September 2013 - 02:14 PM

> Bob Coyle: I don't recommend you do this unless you have some understanding of the chemicals and wear gloves and safety glasses. There is lot's of info on the internet if you want to pursue it.

... and take adequate precautions against the corrosive fumes. I've read of somebody having permanent vocal-chord damage.

This certainly seems to be something that should be done in private, or only with knowledgeable consenting adults.



#11 Isculpt

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Posted 29 September 2013 - 11:35 PM

Thanks Bob, Peter and John.  I'll certainly read up on making ferric chloride before I attempt it!  Can you tell me what color(s) ferric chloride contributes in a pit-fire?  For that matter, what effect does copper sulfate have? I know that personal experimentation is the best way to answer these questions, but pit firing is so labor intensive that I'd rather not spend half a day firing just to create a test tile or two...or even worse, to experiment on a sculpture that I've put lots of time into!  

 

I searched all three guys' galleries hoping to see an example of a pit-fired pot using those chemicals, but no joy. (It was a pure pleasure searching the galleries, though -- John's yakishime with youhen charcoal finish is breathtaking and Bob's electroformed pots are truly fascinating).   Nonetheless, I'm wondering if anyone knows of an image of pit-fired pots using those chemicals.



#12 Bob Coyle

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Posted 30 September 2013 - 10:08 AM

What you get depends on the firing conditions. With ferric chloride you will pretty much get a yellow or orange color on white clay. Copper sulphate will give you a black or grey or (if you are lucky) a reddish blush under reducing conditions.

Do a google search under pit fired pottery and you will get an idea of what it looks like. There are also a few vidios on Youtube to get you started.

#13 JBaymore

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Posted 30 September 2013 - 10:53 PM

(It was a pure pleasure searching the galleries, though -- John's yakishime with youhen charcoal finish is breathtaking ............................

 

Thank YOU!  :D


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#14 Isculpt

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Posted 01 October 2013 - 02:27 AM

What you get depends on the firing conditions. With ferric chloride you will pretty much get a yellow or orange color on white clay. Copper sulphate will give you a black or grey or (if you are lucky) a reddish blush under reducing conditions.

Do a google search under pit fired pottery and you will get an idea of what it looks like. There are also a few vidios on Youtube to get you started.

Thanks, Bob.  Now I'll know what I'm looking at when I visit some pit firing websites.



#15 neilestrick

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Posted 01 October 2013 - 01:20 PM

If you want something simpler and safer, just use salt. Make a super strong saltwater solution using rock salt in a 5 gallon bucket and soak wood chips in it for a day. Let the chips dry out on the driveway and use them in your pit. Lots of nice reds, pinks, oranges and yellows without worrying about chemical burns or blowing up the studio.


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#16 Isculpt

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Posted 01 October 2013 - 02:49 PM

If you want something simpler and safer, just use salt. Make a super strong saltwater solution using rock salt in a 5 gallon bucket and soak wood chips in it for a day. Let the chips dry out on the driveway and use them in your pit. Lots of nice reds, pinks, oranges and yellows without worrying about chemical burns or blowing up the studio.

Holy Moly, that sounds exciting!!!!  Thanks!



#17 firefly

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Posted 01 October 2013 - 05:10 PM

Hi Jayne (and others),

 

I found this excerpt from a Sumi von Dassow video to be very helpful. She gets amazing results!

 

http://ceramicartsda...n-a-pit-firing/

 

Happy firing,

 

Jean



#18 Isculpt

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Posted 06 October 2013 - 12:14 AM

Hi Jayne (and others),

 

I found this excerpt from a Sumi von Dassow video to be very helpful. She gets amazing results!

 

http://ceramicartsda...n-a-pit-firing/

 

Happy firing,

 

Jean

BEAUTIFUL pot, Jean!  And thanks sooo much for this video!  I've searched for something this specific for a long time. I can't believe I now have access to such a wealth of information! Thanks again! 

Jayne



#19 firefly

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Posted 07 October 2013 - 05:41 PM

Thanks for the compliment - I'm wearing my "aw, shucks" face....

 

If you haven't already seen it, the book "Alternative Kilns & Firing Techniques" by James C. Watkins & Paul Andrew Wandless has a lot of information, too, especially if you want to work with ferric chloride. Plus, if you think you may want to experiment with trash can/barrel firing, here is an interesting post from Bonnie Staffel on a clay art thread that I enjoyed reading:

 

http://www.potters.o...ubject90543.htm

 

I promise I'll stop now!

 

Jean



#20 Isculpt

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Posted 08 October 2013 - 09:11 AM

Thanks for the compliment - I'm wearing my "aw, shucks" face....

 

If you haven't already seen it, the book "Alternative Kilns & Firing Techniques" by James C. Watkins & Paul Andrew Wandless has a lot of information, too, especially if you want to work with ferric chloride. Plus, if you think you may want to experiment with trash can/barrel firing, here is an interesting post from Bonnie Staffel on a clay art thread that I enjoyed reading:

 

http://www.potters.o...ubject90543.htm

 

I promise I'll stop now!

 

Jean

Jean, Don't stop!!  Seriously, this is such useful information.  I've read everything I could find & watched youtube videos, but the information is usually very general.  And it's so helpful to know the "why's" of something.  (kind of like giving a fish to a hungry man vs teaching him to fish). This article makes the point that the lower temperatures in sawdust firing can't fume the salt to produce red coloration, which helps me to understand why my trashcan fires haven't worked as I hoped.  I can't figure why Bonnie is putting pet litter sprinkled with copper and salt, as a bottom layer beneath the pots, though.  Any thoughts on that?  Also, regarding Summi's video, I'm wondering about that blower system of Summi's.  I don't think I've seen metal pipes like that, perforated all over with holes.  She says that they only last through 3 or 4 burnings, so they clearly aren't made for this kind of use.  I  wonder where would a person find the kind of metal pipes that she uses?  And I'm guessing that's just a leaf blower or some such thing to provide the air?  Since you created that beautiful pot, would you mind sharing your technique?

Thanks, Jayne






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