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PeterH

Member Since 28 Apr 2013
Offline Last Active Jan 03 2017 02:58 PM
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Posts I've Made

In Topic: Lustre / Reduction Chemistry Question

31 December 2016 - 08:15 AM

Hi,

 

You might like to try this. You will need:

- A metal canister open at one end a little bigger than your pot.

- Two pieces of chipboard big enough to cover the end of the can.

- A brick or two.

- A newspaper about 1/4 inch thick.

- A bucket of water.

- Rubber bands or string.

- Some charcoal.

- A plastic shot glass or similar.

- Some alcohol (UL meths, US ??)

 

- Place the first piece of chipboard on the ground, with the tin on top. (This insulates the tin a bit.)

- Cover the bottom of the can with charcoal.

- Put the newspaper into the bucket of water to soak.

- When it's getting nearly time to take the pot out of the kiln take the newspaper out of the water.

   Let it drip a bit then wrap it round the chipboard and secure it with the rubber bands or string.

   You should have a nice flat region of paper that will securely seal the lid of the can.

- Fill the shot glass with meths.

- Take the pot out of the kiln, and place it in the tin on top of the charcoal. Keep it away from the sides.

- Rapidly:

  - Pour the meths into the tin. [H&S keep your head well clear, and wear something like a leather glove.]

  - Place the wet newspaper over the tin to fully seal it.

  - Put a brick or two on top to ensure the seal it good.

 

WAIT until it cools. Then open the tin. You should be surprised how big a vacuum has been generated,

and the tin should have left a clear compression ring in the newspaper.

 

Hopefully the pot should be reduced.

 

If it was a copper-matte "glaze" you may have reduced it so far that there is a layer of metallic copper. You

can carefully reheat this in an oven and watch the colours develop. Unfortunately they fade with time.

 

PS-1

 

A tin may be too weak and implode with the vacuum. I used stainless-steel tea-caddies from a charity shop.

 

You may want to try reducing the degree of reduction. You might try less meths, open sooner, etc.

 

PS-2 I've explained [sic] my limited understanding of copper-matte glazes in post #5 of

http://community.cer...atte#entry42291

 

PP-3 Dedicated to the memory of Heath Robinson.

https://businessengl...png?w=300&h=211

 

 


In Topic: Your Experiences With Stain/s

31 December 2016 - 06:37 AM

Hi,

 

I seem to have failed to make myself clear.

 

I don't know about "cleavage" numerical value ... from 100-150 or so

Can you reference an accessible paper/article that has such numbers in it?

 

I don't recognise the term optically negative

Can you reference an accessible paper/article that uses the term?

 

That way with some research I should be able to understand your points, and relate them

to my current understanding of optics and crystallography.

 

Regards, Peter

 

Hi,

 

At the moment I'm totally failing to relate your recent posting to my understanding of optics, and my sketchy

understanding of crystallography.

 

What would help me most is references to online papers that discuss the topics you mention.

 

To verbalise my confusion:

 

All minerals have a "cleavage" numerical value ... from 100-150 or so.

- I cannot even image what units these cleavage numbers might be measured in, and I've always thought of

   cleavage and refraction as being essentially unrelated topics (bar the weak relationship through birefringence).

- The only cleavage related "numbers" I can thing of are various cryptographic angles and Miller indices. I had to

   look up the name of the latter, but they are the bracketed triplets describing crystallographic planes; e.g (101).

 

optically negative properties

- A term I'm totally unfamiliar with, although a quick google might suggested that it might relate to birefringent crystals.

- I totally failed to find anything linking "optical negativity" to matte/satin effects. Indeed I'd always believed that these

  were explained by the relative intensities of specular and diffuse reflection.

 

As I said, I hope that reading some relevant papers can help me understand things better.

 

Regards, Peter

 


In Topic: Your Experiences With Stain/s

29 December 2016 - 03:02 PM

Hi,

 

At the moment I'm totally failing to relate your recent posting to my understanding of optics, and my sketchy

understanding of crystallography.

 

What would help me most is references to online papers that discuss the topics you mention.

 

To verbalise my confusion:

 

All minerals have a "cleavage" numerical value ... from 100-150 or so.

- I cannot even image what units these cleavage numbers might be measured in, and I've always thought of

   cleavage and refraction as being essentially unrelated topics (bar the weak relationship through birefringence).

- The only cleavage related "numbers" I can thing of are various cryptographic angles and Miller indices. I had to

   look up the name of the latter, but they are the bracketed triplets describing crystallographic planes; e.g (101).

 

optically negative properties

- A term I'm totally unfamiliar with, although a quick google might suggested that it might relate to birefringent crystals.

- I totally failed to find anything linking "optical negativity" to matte/satin effects. Indeed I'd always believed that these

  were explained by the relative intensities of specular and diffuse reflection.

 

As I said, I hope that reading some relevant papers can help me understand things better.

 

Regards, Peter


In Topic: Raw Glazing At Cone 6-8?

29 December 2016 - 10:27 AM

>"Glazes Cone 6 1240C" by Michael Bailey

>they are rare and not cheap - £12.99 cover price, cheapest on Amazon £34......

 

You can save a little by using one of the bookshops indexed by bookfinder, at the moment the cheapest are £25.16 new, £22.26 s/h.

http://tinyurl.com/j6pbh3m

 


In Topic: Porcelain

28 December 2016 - 08:22 AM

Strange, the Scarva site doesn't seem to give any firing cone or temperature.

http://www.scarva.co...lip/m-5490.aspx

 

Does it say anything on the container? If not, I'd try emailing Scarva (as they suggest under the "Description" tag of the referenced page).