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Tuesday, February 11, 2014

960: A new alloy of sterling PMC

Book made with 960 sterling
For the past year I’ve been working with an enriched version of sterling metal clay. "Enriched" simply means that this alloy has more fine, or pure, silver in it. It's still sterling, and can be legally marked as such.  We're calling it "960". That number refers to the amount of fine silver in the alloy just as 925 identifies regular sterling.  

960 is made by mixing equal parts of PMC Sterling and PMC3. I open a 25 gram pack of PMC3 and a 25 gram pack of PMC Sterling and mix them together. It takes less than 5 minutes. It's really that easy. 


You mix it, kneed it, fold it and so forth until it's uniformly colored.  No water, or oil is necessary when mixing these clays.




This is simple to do because PMC Sterling is a grayish color and PMC3 is more beige. Probably because I've done a lot of cooking in my life, once it’s uniformly colored, I let the mixed clay rest for 1/2 an hour or so.  Enclose it in plastic, the way you would with any other metal clay.



I just taught the first class using this new material.  In the class, at The North Country Studio Workshop conference at Bennington College, the students made their own 960 to work with. It got great reviews.

From left to right: PMC Sterling, 960. PMC3
Although I love the way PMC Sterling handles, it does have a couple of drawbacks, or one major drawback, really; the carbon firing.  Carbon firing is just not fun.  No one likes it and I think it's holding PMC Sterling back from the attention it deserves. It's so much stronger than fine silver PMC, has a longer open working time and superior dry working qualities. But then, you have to fire it, twice, and there's the carbon!

960 is almost as strong (in my opinion), handles almost as well, carves almost as well as 925 PMC Sterling but NO CARBON!  It fires in air on a kiln shelf like any of the fine silver PMCs.  We've been firing 960 at 1500F for one hour.
It has another perk; gold foil, when you keum-boo, goes on more readily than it does on PMC Sterling.  However, it doesn’t diffuse into the silver surface as quickly as it does with fine silver (I guess that’s really two perks).

Is there a reason to continue to have PMC Sterling in my studio?  Yes, PMC Sterling is peerless for that occasional very delicate design that requires extra strength.   It's also, in my opinion, the best way to fire diamonds in metal clay.  Although diamonds will survive an air-fire, the temperature must be quite low or they will not survive.   I like to fire my metal clay as hot as possible so if I want diamonds in a design I will use the original PMC Sterling and I’ll fire in carbon.

How did 960 come about? A year and a half ago I met with Tim McCreight and a few others to discuss PMC Sterling.  On the last day of the meeting we were brainstorming and Tim said, "What if we enriched the PMC Sterling?  By increasing the fine silver content of the alloy maybe we could get rid of the carbon altogether.”
The idea had an immediate effect on me.  It resonated; I went right home and mixed up my first batch of 960 and that's really the only metal clay I've used since then.

Please try it for yourself and let me know how it goes!

Pieces made with 960:


When it's fired and finished, I'll rivet something between the window and the little frame and cover the blank pages with decorative paper.  In air, the pencil burns off.



At this point, after so many 960 pieces, I trust this clay to sinter without distortion, in air, on a kiln shelf.  I'll fire this book soon, but not assembled.  Each page will be laid on the shelf.





84 comments:

  1. I can't wait to try it! What kind of shrinkage are you getting?

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    1. Same as the shrinkage I get with other clays; right about 15%.

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  2. Wow, Celie, this is a fabulous development! I can't wait to try it. I'll be sharing a link to this post in my new Jewelry Making Techniques blog - it's too important not to be seen by the widest possible audience!

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  3. Way to think and work outside of the box!!

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  4. EXCITING!!!!! Thank you for running with this!

    Can you mix Art Clay Fine Silver with the PMC Sterling or do the binders not combine?

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    1. Hi Paula, This is something I have not done so I really can't answer your question. Sorry!

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    2. I have some Sterling on the way, so I shall try it! Worth a shot!

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    3. Chiming in to sayI have mixed Art Clay Silver and PMC Sterling together with no problem. Shrinkage seems to be 13% (after one test on a solid piece for what that's worth.

      Celie, I so appreciate your R&D on this, I know it is time consuming and you are awesome for doing it!
      ~ Holly Gage

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  5. Very exciting. Great idea, mixing the two. Now, to AFFORD those silver prices!!

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  6. I keep wondering if the Argentium people could get on board with a metal clay with a tiny bit of Germanium in it. Then we'd really have the best of all worlds. Tarnish resistance, no fire scale when adding components via fusing or solder, higher malleability when annealed, heat hardening, etc. Do you know if there is any discussion of such a thing?

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    1. I'd love something like that too Vickie.

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    2. Vickie, you KNOW I'm onboard:) Celie, please please please use your glorious influence:)

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  7. Thank you for sharing this great information.

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  8. This is really exciting! Thanks! I'm ordering from Rio tonight. Can't wait to try it.

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  9. I torch fire my PMC3 do you think this can be done with 960?

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  10. Thank you Celie, I am going to try this very soon.

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  11. wow wow wow wow wow!!!!!! I'm so excited. I need more strength, but the carbon is a bummer!!!!!!!!!!!! You are so awesome...never even thought of it!!!!!! Thank you!!! Um...so, I'm exclamation heavy today...Canada's doing well at the Olympics:)

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  12. Thanks Celie for sharing and always thinking outside the box!!

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  13. Very neat indeed! I guess we are going to need a .960 stamp now.

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  14. this is exciting news indeed!
    Just to say though... you can very well fire fine silver in carbon at the max usual temperature. I sometimes do that to protect stones (although not diamonds...). I might try to mix some ACS and Sterling... just to see...

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  15. I'll be giving this a try, it's a really interesting development and may well help those who don't like the carbon firing to embrace wonderful PMC Sterling!

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  16. OMG this just changed my life!!! Cannot wait to try it out!

    Kathy
    Just Sayin' Jewelry

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  17. I have also been playing with a 60/40 mix of sterling clay and fine silver. I have been making a sandwich of fibre blanket and firing them on an open shelf with gemstones, not diamonds though. The clay mix doesn;t seem to need carbon. I quench by dropping the piece blanket and all into cold water about 10 mins after the timer on the kiln goes, hardly need any pickle either.

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  18. fantastic! wondering if it's possible to use pmc + instead of pmc 3? (i have + at home already!)

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  19. Hi WillowTree, That's very interesting. You use the fiber blanket to protect the gemstones and when your just firing the 60/40 mix you fire in air? At what temperature?
    Why do you quench?

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  20. Hi Holly,
    Although I prefer the working qualities of PMC Plus, PMC3 is a lot stronger and therefore a better clay to mix with PMC Sterling if the objective is to keep it as strong as possible.

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  21. Have you tried making rings with it using investment pellets to hold shape and size? I know they work well with fine silver but leave too much oxidation with sterling.

    Thanks!

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  22. Hi Carol Ann,
    I have found the shrinkage of 960 to be a reliable 3 ring sizes so I haven't needed to use ring forms. However, each artist has a a slightly different method for forming rings so it follows that the shrinkage might vary from artist to artist. Once you've figured it out for yourself it should be pretty consistent.
    Best, Celie

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    1. Celie - That's great to know! Thank you! It would be great not to have to rely on the ring forms.

      Carol Ann

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  23. Hey Celie, I'm so excited about this, shared it on my facebook fan page, thanks so much! I use to work almost entirely in PMC3 and now have switched to the sterling, but HATE the carbon aspect. I have a couple questions that I don't think anyone asked yet, if so sorry to be redundant! I work a lot with dried components and currently have lots of these in PMC3 can these be added to the 960 I'm assuming yes. And going further can the pastes and syringe PMC3 also be used with 960 again I would think yes, but since you've been doing this for a while best to ask first, TIA

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    1. This comment has been removed by the author.

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  24. Hi Liz, it's a good question and no one has asked it. I tried to keep my "parts" separate for a long time for the sake of research. After a while (and a certain amount of confusion) I went ahead and mixed the two clays, 960 and PMC3 (so a back sheet might be PMC3 and the bezel might be 960) and it was fine. You need to fire the mixture at 1500F, not higher. That means the PMC3 parts are not as strong as they would be fired at 1650F, but that's often acceptable. Using PMC3 slip is okay but again, 960 is the strongest. I would not use PMC Sterling slip because you'd be over firing it at 1500F and it needs the protection of carbon!
    Hope that's clear enough.
    Best, Celie

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    1. Now just to finish up using all the sterling PMC components I have - then freedom at last from the dreaded carbon ;-)

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  25. Dear Celie, Forever the explorer you have charted new waters. Thank you for sharing your discoveries...

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  26. One other question - Should it be stamped SS 960? Will that be confusing to buyers?

    Thank you,

    Carol Ann

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  27. Hi Carol Ann, Stamping it as 960 might be confusing, you're right. You could stamp it "sterling" or "sterl".
    Celie

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    1. Maybe stamp it as "Fine Sterling" or "Sterling +"? Or "Sterling 960"

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  28. Celie..I know you're a fan of the slower ramp for Sterling. Do you suggest full or slower for 960?

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    1. Hi Sue, I ramp 960 at FULL speed to 1500F then hold for one hour.

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  29. Thank you so much for sharing Celie! This is so wonderful. I loved working with the Sterling but hated the firing and continued using PMC 3 as much as possible. I can't wait to try the 960. You are amazing!!

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  30. Thanks, Claudia. Let me know how you like the 960!

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  31. Thank you so much for your research and for being so generous with your knowledge. This will surely change the way I work. I am so happy!

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    1. Thank you for your comment, Norah. I look forward to hearing how you like it.

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  33. To Celie and all others who have already tried this 3/960 mix: do you think it can be torch fired? Has anyone tried it already?

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    1. Hi Lila,
      I have not torch fired 960. Sorry.

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  34. Hi Celie, I am very excited to try this. I still have not fired any sterling since I took your workshop last summer! I forwarded a link to this to Fred. He and I just had a discussion the other day and he was saying he wouldn't try sterling because of the double firing method. Thanks for being the great innovator and artist!

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  35. OK Celie I'm going for it!!! Ordering sterling and 3 today...wish me luck!!! I'll apologize now if I bombard you with questions!!! Thanks for all your hard work in this endeavor!!!

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    1. Hi Erica, Questions are fine. Have fun!

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  36. Hi Celie,
    Can use Pro with PMC Plus or 3? I have some that I'd never used. Thanks,
    Bernadette

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  37. Hi Bernadette, I haven't made it with Pro. Sorry I can't be more helpful.

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  38. Celie, after reading your blog a month ago I was so excited. Of course I had to wonder as Bernadette, could PMC Pro be used instead of sterling silver, and would I get Sterling? I mixed 25g of PMC Pro and 25g of PMC 3. I got impatient so I torch fired.... And... Perfect. No fire scale. So I'm thinking that the 90% silver of the PMC Pro and the .999 of the PMC 3 produce something higher than Sterling. I even hammered my test pieces. So I made more... Same outcome. I'm wondering if your mixture is higher than 960? I called mine Frankenclay ;) lol! Since I have no clue what content it is but its strong and torchable!

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  39. Great research, Seavbeach. However you need to remember that Pro is being discontinued so enjoy your alloy while supplies last...
    Best, Celie

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  40. Celie, good point! I've had the package for a year and a half and didn't know what to do with it until I read your blog! I wonder if I was the only one? I'm glad your wheels were spinning to give me this idea to try and finally open the package that stared at me every time I walked into the studio.
    Thanks!
    Anise

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  41. Have you tried using gold paste on 960? I am receiving my first 925 in the mail today so that I can combine with pmc3, really looking forward to the new alloy. I have used Aura 22 on pmc3 for years, I paint 2 layers on the piece prefiring, then out of the kiln, before any brushing or tumbling, I add 2 more layers and torch for a couple of minutes, and immediately burnish, while hot, to ensure good adhesion...gives a deep bright gold finish after tumbling. I would like to do this with 960 too, just wondering if anyone has tried it?

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    1. had to post as anonymous since i am not a member of the others, but i am, Lynn Cobb, not "anonymous" :)

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  42. Hi Lynn, I have not tried Aura myself but I think Tim McCreight may have used Aura on 960. It should work!
    When you say.." I paint two layers on the piece pre firing " can you say what you mean by that?
    Let me know how you like the 960 and how the Aura does.
    Best regards, Celie

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    1. Lynn Cobb here: in the greenware stage, before firing, I paint a layer of gold paste, allow to dry, then add a second layer, dry and then fire in kiln. Before brushing or tumbling, I paint on another 2 layers, drying between, and then torch for a minute or two. While still hot, I burnish...I get very good adhesion, and a very deep bright gold with this process, and hope that it will work with 960 also...thanks Celie!

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  43. Celie, I am very excited to finally experiment with 960 today! Can I solder fine or sterling silver bezel wire to a base post firing? I am looking to set some natural gemstones to bracelet components.

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  44. Hi Monique, Yes, you can solder to base findings.
    Best, Celie

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  45. Hi Celie, Have you tried firing any stones in place with the 960? I am wondering if 1500º is too hot for sunstones or synthetic or lab grown stones? Thanks.

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  46. Hi Barb,
    Various people have experimented with stones in different metal clays, and fired at different temperatures. If you look on-line you'll be able to find more information about that. The only work I've done is with diamonds in PMC Sterling, fired in carbon.
    But I know the information is out there.
    My best, Celie

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    1. Thank you Celie. It looks like 1500º will be too hot for the stones I'm thinking of. I'll try a sample and see what happens.

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  47. Celie,

    I read through all the comments and didn't find an answer to my question. I make thick pendants from PMC and them DOME them after firing. I found I needed to fire them for 3 hours at 1675 degrees in order for them to be strong enough to bend smoothly without cracking. If fired less time or lower temps, I got cracking consistently.

    I just made 6 very thick pendants using PMC and Sterling. Are you sure I can't fire them higher than 1500 degrees for longer period of time? I need to dome each one of them after firing.

    I have not had good success with firing them in dome shape first. Results come out warped, or design is distorted.

    Please help as these are custom orders and I have no time to experiment.

    Virginia Vivier
    www.Etsy.com/EspritMystique

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  48. Amendment to my last (above) comment/question. I DID fire the thick pieces of PMC+Sterling at 1550 degrees for 2 hours and they came out almost all the way through as solid silver. When I drilled a hole in the thickest one, I could see some black binder come out, but for the most part it fired through.

    I did try to "dome" the thinnest of the 6 pieces and one came out fine. Another one was beginning to crack on the back, so I stopped the doming process and smoothed out the crack with a tool so it didn't show. The crack did not go through to the front (fortunately). I can dome them with my Bonny Doon Press, or by hand and get the same results (cracking) with thick pieces. Should I anneal them first?

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  49. Hi Virginia,
    I have not done extensive testing using a range of temperatures for the 960. It sinters at 1500F and it's strong so I haven't gone further than that.
    It sounds to me as though your kiln may be a bit off. It also sounds as though you have figured out what you needed to know.

    Yes, you can anneal them but if they are too thick you will still have a hard time doming them. You'll probably be better off making them thinner.
    Best, Celie

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  50. I am very interested into doing this as well! Are they really high temperature alloys? It is amazing what you can do with them. http://www.jamesduva.com/product-specifications/

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  51. I think I have never seen such blogs ever before that has complete things with all details which I want. So kindly update this ever for us. click over here

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  52. Dear Celie,
    I really like to work with 960 for all positive it combines. For some reasons I decided to fire for 2 hours a ring and it shrank 5 sizes (from 11 to 6 for a regular size ring)... So I guess that there is not a full sintering after 1 hour... (I also had a 3 sizes shrinkage after one hour)...
    I could make the ring larger to size 7 but ... I still have to re-do it for the right size...
    Respectfully, Caroline

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  53. What a wonderful blog! Thanks for sharing! I'm new to the world of PMC. Just ordered my first batch of PMC3. I love the idea of mixing in the sterling. Has anyone tried to torch fire the 960?

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    1. Yes, you can torch fire 960, but I always recommend kiln firing for greater strength.

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  54. Thank you so much, Celie! I think your work is amazing! :)

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  55. I'm making a link bracelet 8 cards thick. Should I hold at 2 hours so it sinters all the way through? What kind of shrinkage percent can I expect?

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  56. Really interesting post. Worth to read. I was completely unaware about this new alloy of sterling PMC.

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  57. I've been firing 960 silver clay in my kiln for some time with great results. Even though I can fire 960 without using carbon, I'm not clear on whether I can solder a fired piece without using silver solder & flux, or if it needs to be put in pickle. Will soldered 960 have firescale?

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  58. I have not worked with metal clay for a few years but am ready to start up again. I've been out of the loop completely. Can you get the beautiful smooth finish the jewelers get with the product? I have been able to get it on all my .999 fine silver pieces but don't want to invest in this if I can't get it with this mix. Thanks so much. Colleen

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  59. Hi
    It all looks so wonderful here, but....
    I just opened two packages of clay and mixed it to obtain PMC 960. While I was mixing it, it was already drying. Then I tried to form a ring and...it was COMPLETELY IMPOSSIBLE!!
    It cracked and was too dry to do anything.
    It looks impossible to make anything nice within 4 minutes , so how to make it flexible again instead of throwing 95$ to the garbage ???
    Thank you

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  60. Hi Jasnie, Assuming you mixed PMC3 and PMC Sterling 925 to get PMC960 perhaps you took a bit longer to mix it? This simply requires a rest period in a hydrating environment (like a cup with a damp sponge in it with the loosely wrapped 960). Other thoughts: do you live in a very dry climate? Again, once the clay has rested a bit in a hydrating environment it should be fine to work with. There's no reason to throw it out, ever! PMC can always be rehydrated. Don't try to make something if the clay seems dry. Wait until it's rehydrated. Hope this helps, Celie

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