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Member Since 02 Jan 2012
Offline Last Active Feb 13 2015 09:36 AM

#46714 Kiln Flue Gas Analysis

Posted by Frederik-W on 27 November 2013 - 06:12 AM

I built a system like that for a gas kiln,

but the results were not very good because the sensor was situated in the kiln flue and the flames made the readings fluctuate a lot.

Also the common (cheaper) variety of sensors are very non-linear - i.e. they are designed to go from hard-on to hard-off, and you do not get much in-between. So the accuracy of your readings suffer.

I still want to improve on this but I am too busy with other things at the moment.

The newer "wideband" type of sensors are accurate and give a more linear output put the electronics to build one is more complex and if you buy a ready-built one (for cars) they are quite expensive (for someone like me).

#45564 Gallery Commentary?

Posted by Frederik-W on 12 November 2013 - 05:48 AM

It is still not fixed.

I just added a comment to Phill's work and got the

"Your comment requires moderator approval before it will be shown".

#45065 Covering Up A Crack In Bisque

Posted by Frederik-W on 03 November 2013 - 07:14 AM

Just to let those who might be interested know:

The crack mended beautifully. No sign of it after firing. (Earthenware).

It was a patch slurry made of paperclay and "Patch-A-Tatch".

So it was either the paperclay or the "Patch-A-Tatch" or both that did the magic.



A lot of people seem to think (probably with good reason) that it is not worth the trouble to try and fill cracks because it will probably get worse and it is easier just to start over. Especially with higher-fired stuff such as stoneware or porcelein it is apparently more difficult.

However it is not a satisfying answer for something which took a lot of time & very hard work. I wish there was more technically-explained solutions that will work.


I will share the little information I have:


There is a product by Duncan called "Patch-A-Tatch".

"ceramic cement used to attach or repair greenware or bisque".


I know this works for attaching pieces that have broken off, e.g. handles etc, but I have not tried it for cracks. I think it is some kind of mixture that melts and fuses the two pieces together when fired. (Ceramic "Flux")


I have read about using the same phase of clay as in the original piece, e.g. if it is bisqued, then grind up bisque pieces and patch it (do not use raw clay to patch a bisqued thing). This makes sense to me because the shrinkage rates should be the same.

So it might be worth a try to mix pieces of ground bisque with e.g. Patch-A-Tatch or some kind of "flux" or paperclay slurry.


I know that paperclay has an amazing ability to attach to dry clay or even bisque. When it dries it does not shrink as much due to the paper fibres and it attaches better.


At the moment I am trying to fix a crack in greenware with paperclay. I have mixed the same type of clay with a bit of toilet paper to a slurry. Often people advise to mix in a bit of vinegar. The patch worked well but I still have to fire it. I fire only to earthenware temperatures so maybe I have a chance.

I will post the results in a week or two.

#45063 What's Wrong With Big-Runney Feet?

Posted by Frederik-W on 03 November 2013 - 06:42 AM

In Art there are no rules.

There are guidelines yes (but you don't have to follow them), and there is bad taste, there is pretention, there is rubbish etc, but no rules. Some things just break all the rules but the way it hangs together is just beautiful or meaningful. Do not let pedantic people who are set on rules cramp your creativity.


For craft things are a bit different, especially if you work within a tradition. If you make pots in a certain cultural style or tradition then you have to follow the customary rules (most of the time).

#41351 Why Earthenware?

Posted by Frederik-W on 23 August 2013 - 11:08 PM

Earthenware requires far less energy to fire,

so you save on electricity, you save on greenhouse gasses and you help save the planet.

Your kiln and kiln elements will last much longer with earthenware.

Many colours come out brighter for earthenware.

Bisque and glaze firing temperatures for earthenware are so close that you can sometimes combine green and glaze ware and in one firing.


Many potters fire stoneware by default, for no good reason. What a waste.

#41350 New Regs On Silica Dust

Posted by Frederik-W on 23 August 2013 - 10:46 PM

There is no reason for potters to get paranoid.

A bit of common sense is all that is necessary regarding dust.

We have dwelled on this topic before.


The workers that are affected are primarily those in construction (90%)

"... during work with stone, concrete, brick or mortar. It can occur during sawing, grinding and drilling and is common in glass manufacturing and sand blasting".


Furthermore the rules are just a proposal at this stage. In the USA.


Now go ahead and stone me for warning against paranoia in the potters studio,

I just hope a bus does not hit you when you cross the road.

#41004 Natural Talent....

Posted by Frederik-W on 18 August 2013 - 05:53 AM

You labour on a piece of work, you strain yourself and spend hours,

then when you think you have really done well ...

... you see someone else who made a similar thing, only vastly better, with no effort and in no time ...


#37406 Second bisque firing

Posted by Frederik-W on 20 June 2013 - 06:03 AM

I agree with Jim. Don't waste time, electricity & generate unecessary greenhouse gas.
Let the sun dry your stuff when you can, then fire them as quick as you can - bearing in mind thick or uneven pieces.

#35150 Firing times

Posted by Frederik-W on 18 May 2013 - 09:13 AM

I guess it boils down to how often do you like to change the heating coils and relays in your kiln Posted Image
I am new to pottery and "magic" of kiln firing but what I have read and told by people with years of experience - faster you heat up, faster you burn out the heating coils/wires. Simple physics.

Hi Mart, you are correct about the switching relays/contactors deteriorating because they switch more often during a slow firing.
However I do not think you waste the elements more during rapid heating.
Most kilns that I know switch the elements hard on & off to control the temperature. More "off" periods for slow heating and more "on" periods for faster heating.
The elements do not go to a higher temperature during fast heating (they still get the same voltage), they just stay on longer. (less "off" periods)
However the added-up on-time will be less during a quick firing because the kiln does not waste time to loose as much heat.
So if the elements deteriorate because they are used more, then a quick firing will actually be better,
Unless there are other factors involved, and if there are I am happy to learn about it.
I think all the electricity you save with rapid firing will also help to buy new elements.

What may make your elements deteriorate more is if the atmosphere in the kiln has moisture or other gasses that add to corrosion/oxidation of the elements.
e.g. if you fire greenware with all bung holes covered from the start.

#33260 How envy killed the crafts

Posted by Frederik-W on 20 April 2013 - 04:29 AM

Back in the last 1/4 of the 19th century when architectural terracotta was booming, they fired the ware in huge beehive shaped kilns, fired with wood.

Very interesting. I like big sculptures and I like Terracotta and I'm experimenting with wood fire but I do not have the space in my suburban backyard for a big wood kiln.
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#31401 ..and what is this?

Posted by Frederik-W on 22 March 2013 - 05:24 AM

"Sotheby's said the bowl is a "remarkable and exceptionally beautiful example of Song pottery, celebrated for its thin potting, fine near-white body and ivory coloured glaze".

$2.2 million paid.
I think it is ugly. It is at best very plain.
It is one thing to have cultural/historical value or technical merit for what was achieved 1000 years ago, I do not doubt that, but it is still ugly.
The value of something in monetary terms has never been a good indicater of artistic merit.

#28745 How envy killed the crafts

Posted by Frederik-W on 01 February 2013 - 08:17 AM

What an absolute brilliant opinion piece by Garth Clark!

The distinction between between art and craft is a very real and useful concept!
Sometimes the distinction is vague but that does not mean there is no difference.
The problem if i uderstand him correctly, is not that craft has no value, it is that craft tried to be something which it is not, i.e. art.

Some quotes from Garth's article:

"..craft did die from the toxicity of art envy.."

"Resistance to this notion [that craft was really art] was blamed on fine art's elitism but rarely
did one hear the argument and simple truth that it was so because craft was finally, and beneficially, different".

"Craft has been overdosing on nostalgia ..". Some degree of this "ye olde craftsman" romance is unavoidable in craft. Used with restraint it can add charm and a rich connection to the past. But when it is overdone it turns into syrupy restoration village sentimentality".

"Compared to art and design, craft is so marginalized that it is practically irrelevant".

"Design is undermining the craft market at every level. It can deliver handsome ceramics, fabric and jewelry at low cost. It can produce work that to the average eye seems to be handcrafted and can program machines to produce objects that are to some extent, unique".

#24513 The Useful Critique

Posted by Frederik-W on 01 November 2012 - 07:40 AM

I question the dichotomy between a "useful", "good" or "meaningful" critique and the implied other types of meaningless critique (whatever that may be).

I also question the assumption that a critique demands time and effort.

A simple to-the-point comment or honest opinion can be profoundly significant and can be enough to give an artist the direction he/she needs.

Imagine a potter who struggle for years to find out why her pottery is not valued, and people are loath to comment (like so many of you), or people beat around the bush. One day someone who sees her work on her profile gallery makes the comment: "
You are very creative with your form, but your glaze turns your work into kitch". One accurate, honest comment, albeit a bit brutal. That might be exactly what she wants to hear, it might be enough for her to start focussing on her glaze. It might give her the direction she needs, changing her life as an artist. Life is full of stories of people who suddenly saw the light in their careers, love-life etc after one simple but accurate comment, often by a stranger.

I also reject the assumption that all "meaningful" critiques need some kind of ongoing relationship/involvement/time or are of the mentor/student type. That is the way you usually learn a craft, but in terms of aesthetics we can give someone very good feedback without such involvement. E.g. When you exhibit your work it will be judged immediately and harshly, by all kinds of people and as an artist you need to appreciate all such opinions.

#24438 The Useful Critique

Posted by Frederik-W on 31 October 2012 - 09:03 AM

To Wahine/Chantay:

I sympathise with you if you received "dribble" instead of critique.

However I disagree with you if you think that "talented and highly educated persons" are more entitled to provide critique, and are above "dribble".
It smacks of snobbery.
I have read plenty of art reviews where higly educated "critics" provide nothing more than dribble, only difference is that they dress it up in academic pretense.
The fact that someone produces beautiful pieces of art, does not necessarily make him an art critic.
The fact that someone with experience and technique can give you good practical advice does not make him any better in terms of providing an opinion on aesthetics. You can make a very good pot and it might have little aesthetic appeal.

Art history is full of examples of talented artists who were not appreciated at the time by the critics and the people who were supposed to know.

#20457 Environmental Impacts of what we do.

Posted by Frederik-W on 11 August 2012 - 05:00 AM