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Scoria (lava dust) added to a clay body


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#1 jrgpots

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Posted 15 March 2013 - 09:58 PM

I live at the base of a cider cone and have collected scoria dust. This is the dust from lava cinders. It is basically ground basalt. I want to add it to Laguna's 50/50 cone 10 clay body. I don't know how much it will decrease the maturation temp of the clay body. Since scoria has a large amount of iron (12 - 17 %), I'm hoping it will give me a nice speckled pattern or even darken the entire clay body. Does anyone have any experience with this type of homemade basalt clay mix?

#2 bigDave

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Posted 16 March 2013 - 10:30 PM

I have lots of fine scoria also, Im wondering the exact same thing

All I can find is it melts at 1200-2400 F, arrg,

test some and so will I and we can compare notes

#3 jrgpots

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Posted 26 March 2013 - 10:38 PM

I live at the base of a cider cone and have collected scoria dust. This is the dust from lava cinders. It is basically ground basalt. I want to add it to Laguna's 50/50 cone 10 clay body. I don't know how much it will decrease the maturation temp of the clay body. Since scoria has a large amount of iron (12 - 17 %), I'm hoping it will give me a nice speckled pattern or even darken the entire clay body. Does anyone have any experience with this type of homemade basalt clay mix?


Well, I added scoria dust to Laguna 50/50 clay body, threw a small bowl, and fired to bisque (cone04). The scoria did not melt or leave any iron spots. I understand cone 5 is around where basalt should melt (1200 degree C) .....I hope. I will leave part of the bowl unglazed, one third glazed with an opaque cream, and one third with clear glaze. If it works, I'll post a pic.

#4 bigDave

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Posted 27 March 2013 - 11:15 PM

cool, I have one in process drying, you are week ahead or so,

very interested and hopeful for some cool blacks specks or spots or sumptin'

thanks for the update

-big D

ps. how fine is your dust. I am using the fines that come thru a window screen. This is a part of my soil/substrate for bonsai growing. I use lots of scoria but have tossed the fines in the garden for 20 years, then go and by grog and iron ox etc by the bag.

Been wondering for a long time if could substitute this material for iron or manganese, or grog ? So we will find out soon right

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#5 jrgpots

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Posted 28 March 2013 - 12:23 AM

cool, I have one in process drying, you are week ahead or so,

very interested and hopeful for some cool blacks specks or spots or sumptin'

thanks for the update

-big D

ps. how fine is your dust. I am using the fines that come thru a window screen. This is a part of my soil/substrate for bonsai growing. I use lots of scoria but have tossed the fines in the garden for 20 years, then go and by grog and iron ox etc by the bag.

Been wondering for a long time if could substitute this material for iron or manganese, or grog ? So we will find out soon right



#6 jrgpots

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Posted 28 March 2013 - 12:39 AM

I got about 5 gal of fines and ran part of the bucket through a 40 mesh sieve. I got tired after collecting about 4 lbs. I have two colors of the scoria. The first and the one I used for this experiment was red. The second color is black. I thought if I got good color with the red, I should get great color with the black. If it works I will be doing serial testing to find out the best ratio of scoria dust. I'll be glazing in the morning and firing in a few days. Hopefully we'll have color. I also want to try basalt glaze. The scoria is low in silica, so I was going to add a bit silica in addition to some bentonite and a flocculent.

We'll see what happens.

#7 bigDave

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Posted 28 March 2013 - 11:19 PM

If it works, I'll post a pic.


Cant wait

#8 AtomicAxe

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Posted 29 March 2013 - 10:13 AM

You make me want to test this.

the fine grounds probably won't produce considerable speckling, and the particles you want to test with are going to be the particles between the 10 mesh and 40 mesh. Easy enough to do, just mesh 10 mesh first, then follow with 40 mesh, and what is left behind is your granular scoria, which not only should produce speckling, but also fluxing as it melts out of the body, which in minimal quantities should not affect the porousness of the clay if in small quantities, but could be interesting if embedded into the clay surface after throwing (sort of just sprinkled onto the clay when the slip is still present on the surface for example like ash flashing. the fine particles could be interesting in a slip, since it would not affect the clay body, but probably achieve your speckling if in substantial quantity without being lost inside the claybody itself.

#9 bigDave

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Posted 30 March 2013 - 12:03 AM

You make me want to test this.

the fine grounds probably won't produce considerable speckling, and the particles you want to test with are going to be the particles between the 10 mesh and 40 mesh. Easy enough to do, just mesh 10 mesh first, then follow with 40 mesh, and what is left behind is your granular scoria, which not only should produce speckling, but also fluxing as it melts out of the body, which in minimal quantities should not affect the porousness of the clay if in small quantities, but could be interesting if embedded into the clay surface after throwing (sort of just sprinkled onto the clay when the slip is still present on the surface for example like ash flashing. the fine particles could be interesting in a slip, since it would not affect the clay body, but probably achieve your speckling if in substantial quantity without being lost inside the claybody itself.


Good stuff A-Ax, thanks for the ideas,

you seem to know about everything...good job

#10 jrgpots

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Posted 10 April 2013 - 02:50 PM

This is just an update on my project.

1. Laguna half and half clay body.

2. screened red scoria through a 40 mesh.

3. fully mixed 70 gm of this scoria dust to 1500 gm of the clay body.

4. bisque fired the bowl thrown with the mixed clay.

5. Glazed with Laguna oatmeal on 1/2, layered clear on the oatmeal as well as the raw bisque, leaving 1/3 unglazed.

6. fired to ^5.


The clay body looks like "cookies and cream" and shows very nicely with a clear glaze. It did not interact much with the opaque oatmeal glaze. It should look nice under a celadon or other transparent glaze. I want to see what happens if I fire to ^6.



#11 bigDave

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Posted 12 April 2013 - 09:23 PM



The clay body looks like "cookies and cream" and shows very nicely with a clear glaze. It did not interact much with the opaque oatmeal glaze. It should look nice under a celadon or other transparent glaze. I want to see what happens if I fire to ^6.


thanks JRG for the update. We had about the same results.

1st--I mixed about 10 % of scoria dust, stuff fell thru window screen, into laguna b mix. Where it was sponged ..cookies and cream

otherwise,,,not. Cone 5 didnt even ome close to melting it

2nd bout the same in morrocan sand casting slip...smooth out side some scoria rose to surface inside....less than exciting

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