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PeterH

Member Since 28 Apr 2013
Offline Last Active Today, 02:10 PM
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Posts I've Made

In Topic: Hydrometer - Trying To Get The Hang Of This!

Yesterday, 10:21 AM

So in glazing I get information that says glaze should be around 140 to 160 sp gr but the readings are for 1.xxx.

 

I think that somebody has lost a decimal point from the 140 & 160 figures. [*]

As a point of reference the sg of lead is 11.35, so figures over a hundred are definitely unrealistic.

The 1.xxx figures do sound like sg readings.
 

http://digitalfire.c...ic_gravity.html

Glazes do not have a universally desirable specific gravity range like casting slips. The same glaze can be used effectively by different people and in different processes having quite different specific gravities. We have seen glazes with a specific gravity approaching 1.7, others at less than 1.4. This is not only due to the difference in glaze materials and the way they suspend and interact in the slurry, but it is also common for people to add flocculants and deflocculants to glazes. Here is an example of the instructions for one commercial glaze sold as a powder:

 

The 0-70 scale sounds like it might be measuring in degrees Baume.

e.g. see https://www.aardvark...cts.php?cat=398

Degrees Twaddle is another relic from the past you sometimes see used, especially for sodium silicate.
 

Regards, Peter

 

* Of course if somebody is writing down (or calling out)  lots of figures in the 1.xx range

they may find it easier and less error-prone to leave the decimal point as implied.


In Topic: Luster Crackle

24 April 2015 - 09:57 AM

I'm a little confused, by the wording of your query. Are you after wide (>1mm)

cracks in a resinate luster?

 

If so, I've always believed that it was done with "painterly" effects. That is

crackle-paint style magic resulting in the luster layer being in its crackled

state before firing.

 

I believe that there are quite a few painterly tricks-of the-trade (including spraying

drops of meths onto the wet luster) that I'd love to read about.

 

 

Added: Not quite what I was thinking of, but see:

http://www.scarva.co...Coat/m-629.aspx

... especially click View Larger Image then select the image of 7 vases


In Topic: How To Avoid Thin Porcelain From Breaking?

24 April 2015 - 09:07 AM

Lala, does the layer of glue+plasticiser cause any problems in joining the sheets?


In Topic: Thickening Glaze By Removing Water From Surface

02 April 2015 - 02:58 AM

please tell me the meaning of the letters nbsp that you have repeated so many times?

 

&nbsp isn't an intentional word, it's a formatting "character" that's crept in by mistake.

http://www.sightspec...w_faq/nbsp.html

 

... possibly caused by cut-and-pasting from a WYSIWYG editor into the posting.

 

added ... I suspect that use of the "more reply options " button before posting would

reveal this sort of problem in the "post preview" window, and enable the offending

"characters" to be removed before posting.


In Topic: New Copper Carb A Way Different Color!

19 March 2015 - 06:33 AM

so the lighter color green has the MOST copper?

 

 

Looking on wikipedia I get:

 

Azurite has 3 copper atoms in a formula weight of 344.67. 344.67/3 = 114.89

 

Malachite has 2 copper atoms in a formula weight of 221.1. 221.1/2 = 101.55

 

So (114.89/101.55) = 1.13 grams Azurite would replace 1 gram of Malachite