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Member Since 28 Apr 2013
Offline Last Active Today, 07:10 PM

#96037 Cut, Spiral Bit Warped In Kiln

Posted by PeterH on 19 November 2015 - 04:10 PM

I'd been wondering about a variant of Chris's idea. Fire fully-cut and unglazed to cone 6

with the pot resting on its rim. Looking at the first picture most of the slumping seems to

be happening near the rim. (At the least you are reducing the spiral by its thickest 1800.)


Then low-fire glaze.  BTW glazing a vitrified pot can present problems, unless you are

using a "painting" glaze full of gums.

#95703 Making Sodium Silicate.

Posted by PeterH on 11 November 2015 - 07:47 PM

Seems like a high water content.  Is that normal?


UK suppliers seem to sell "sodium silicate" in two strength 75 & 1400Tw  (degrees Twaddle).

Personally I found the 140 to be very difficult to handle and measure. Haven't tried the 75,

buying Dispex last time I needed a deflocculant.


IIRC most recipes just say sodium silicate and don't give a strength. I've no idea what strength(s)

are normal in the US.


Of the URLs given in this thread so far:

- the Axner ref gives a trade-name but no strength, although recommending diluting 50:50 with water

   - a MSDS for the brand gives a s.g. of 1.39 [=780Tw?] http://www.muirbeach...um_silicate.pdf

- the Mistral ref is 750Tw

- the pure-water refs don't seem to give a strength

- my APC Pure ref gives a strength of 82-860Tw


So this is the strength I would buy for use as a deflocculant (or dilute a more concentrated form down to).


However I'm delighted you asked the question because I realise it probably isn't the right strength for the original poster.

Who said in a later post: I wanted to experiment with it as a refractory glue.


So I now realise that he probably wants/needs the sodium silicate as strong as he can get it.  I haven't done a full

search but as a guide Bath Potters offer 1400Tw at £3.14/500g & £23.08/5Kg; unfortunately plus P&P (£3.70 & £10).



If you do go the DIY route have a look at the price of the silica-gel cat-litters (may have to: pick indicator crystals out,

and dry in the oven).


Watch the H&S. I have regarded caustic liquids a lot more warily since seeing a note pinned up in a wet-chemistry

lab saying that somebody in another commercial lab had managed to dissolving part of his eyeball with N/10 NaOH

(he recovered). N/10 NaOH is/was the standard titration strength and is pretty weak (0.4%?), so stronger, stickier

and hotter solutions deserve careful handling.

#95513 Making Sodium Silicate.

Posted by PeterH on 08 November 2015 - 05:35 PM

With prices as low as £8.75 for 1litre inc P&P it hardly seems worth the effort (but if it's fun...).


... advertised with a surprisingly full specification


Moderately interesting document at:

http://www.pqcorp.co...NG oct 2004.pdf

#95396 Home Made Kiln Controller

Posted by PeterH on 06 November 2015 - 06:57 PM

Also dropped a lot of readings and gave me a value of 'nan' not sure what that means yet.


NaN = Not a Number



It's basically a great way of handling those embarrassing situations such as an unanticipated divide by zero.

The NaN propagates through subsequent uses of the variable.

#93954 Cat Walked On Keyboard, Type Too Small To Read, Need Fix

Posted by PeterH on 08 October 2015 - 12:12 PM

Joseph F. wrote

hold ctrl key(bottom left)  and roll your mouse wheel. its probably zoomed.



... reminds me of the time my Unix main window finished up black characters on a black background.

#91435 Weird Liquefied Slip ....

Posted by PeterH on 26 August 2015 - 08:37 AM

What would be the results of adding too much SS?


See the first graph in


#91129 Using Fresh Leaves For Making Molds

Posted by PeterH on 20 August 2015 - 07:23 AM

nancylee: Haven't tried this myself, but the following suggests that one way is to make a

negative impression in plaster, then take a latex positive from that.


Using a big leaf.


Pre-treating leaves to flatten them.




#90796 Pie Dish Dilemna - Rough, Porous Clay

Posted by PeterH on 13 August 2015 - 01:11 PM

Might be worth collecting some of the droppings on a sheet of white paper. It would serve

as evidence, and could help the potter investigate what was happening.

  • Min likes this

#90599 Onion

Posted by PeterH on 10 August 2015 - 03:48 PM

A few pix of sculptured onions, in case it give you some ideas.


http://www.stajcar.c...alia Greens.htm


I quite like the chunky shoots of the first, and the horizontal format of the next two.


#86800 Thinning Slip Water Or Deflocculant?

Posted by PeterH on 09 June 2015 - 04:32 AM

This video may be of interest, especially from 3:50

#77279 Can I Swap Neph Sy In This Glaze?

Posted by PeterH on 13 March 2015 - 09:07 AM

I checked packaging and it is just labelled 'Soda Feldspar' as supplied by CTM in exeter

If it's any help to the discussion here is an analysis from CTM's site

http://www.ctmpotter...elspar Spec.pdf

#76564 What Causes Glaze/clay 'tide Mark'?

Posted by PeterH on 02 March 2015 - 06:42 AM

I bought a pot in Cornwall a few decades ago, which appears to have a dolomite glaze over white stoneware body.

Interestingly it seems to have not a tide-mark but significant areas of the browny-orange.

Attached File  _vase_cropped_10cm.jpg   101.28KB   1 downloads


Looked at more closely the areas appear speckled but free from edge-effects.

Attached File  _vase_detail_10cm.jpg   47.94KB   0 downloads


Any ideas what's happening? I go along with the solubles/volatiles theory for the

previously described tide-marks. Perhaps the pot was dipped and finger-wiped,

distributing the solubles uniformly over a significant [unglazed] area?


PS Chris your example seems to show both tide-marks and more solid areas. Would

you like to comment on any differences in treatment?


  • oly likes this

#74625 Does Anyone Else...

Posted by PeterH on 01 February 2015 - 09:47 AM

Unfortunately all the hand balms you are talking about are not available here in Switzerland.


FYI these seem to be available via your local ebay.


Working Hands



Bag-balm in a square tin


#74152 Sycamore Pottery Is Selling Red Copper Oxide, Anyone Have Info

Posted by PeterH on 26 January 2015 - 03:18 PM

Red copper oxide is coated with a waxy substance keep it from oxidising in the air. So you will

probably need to add a drop of detergent before it will wet. 

#72164 Trying To Find A Square Plate Mould

Posted by PeterH on 20 December 2014 - 07:43 AM

... and there are always drop moulds