[neilestrick]

JKRosenberg, on 21 April 2011 - 06:28 AM, said:

Would epsom salts work as a substitute for sodium silicate?

Sodium Silicate is a deflocculant, meaning it causes particles to repel each other, thereby making a suspension more fluid without adding water. Most often used in casting slips, because with less water the slip dries faster and shrinks less. Epsom Salts are a flocculant, causing particles to bond to each other. Most often used to keep glazes in suspension.

[weeble]

I can't say I have experience with majic water, but basic chemistry makes me doubt you want to substitute it in the recipe... the recipe calls for soda ash, which is alkaline, and sodium silicate is alkaline, but vinegar is acidic. The combination of sodium silicate and vinegar would be... non productive at best... What I'm finding online indicates the two together will just gel up.

HOWEVER, you can use vinegar alone in a lot of the ways I've heard majic water being used. I've used it doing repairs, it works better than plain water.

[ClayToTheCore]

bciskepottery, on 28 December 2010 - 01:16 PM, said:

Lana Wilson's Magic Water recipe is:

1 gallon water
3 tablespoons liquid sodium silicate
1 1/2 teaspoons soda ash

Interesting, I was mixing up some terra sig today, and the recipe calls for equal parts sodium silicate and soda ash as a defloculant. Sodium silicate is an interesting material; it is also known as 'water glass', and indeed, it forms a glass-like surface that will cut you when dried. It is used in radiator sealant, in that when it reaches a hot area (like a leaky head gasket), it fill harden into a glassy material.

[morah]

Isn't there any way to repair broken pots with ingredients that are readily available in your local drugstore? I have no access to the chemicals you keep mentioning. Thanks

[pattial]

morah, on 28 February 2013 - 07:05 PM, said:

Isn't there any way to repair broken pots with ingredients that are readily available in your local drugstore? I have no access to the chemicals you keep mentioning. Thanks

I've had luck using plain old vinegar. My first teacher taught me how to attach handles on cups with it. I still use this method and have great success with it

[morah]

pattial, on 28 February 2013 - 07:40 PM, said:

morah, on 28 February 2013 - 07:05 PM, said:

Isn't there any way to repair broken pots with ingredients that are readily available in your local drugstore? I have no access to the chemicals you keep mentioning. Thanks

I've had luck using plain old vinegar. My first teacher taught me how to attach handles on cups with it. I still use this method and have great success with it

That sounds more like it. Do you use straight vinegar or mix it with something? Will any type of vinegar do?

[weeble]

I just use plain old apple cider or white vinegar, straight. Its not perfect, but I mix a bit of bone dry clay with the vinegar to make slip, then dab a bit of the vinegar on both broken surfaces with a brush, and then quickly use the slip to re-attach. I figure about half the time it works perfect, the rest of the time, well, you might have to futz with it.

And, just to throw you, I've seen sodium silicate at the local drug store, its sold as 'Egg Keep.' And Soda Ash is Sodium carbonate, and is sold in various forms, as 'washing Soda,' for water softener, or to raise pH in hot tubs. These are not really that hard to get, although getting them through a pottery place will help insure you haven't got something added in to make it smell pretty!

[pattial]

When I repair a piece I mix the white vinegar with a little slip. When I attach a handle I score the pieces and just use straight vinegar to attach.

[Mark McCombs]

What is the purpose of the Acetic acid?


Is it to solubilize Sodium and Calcium on the clay-body surface or slip to help the pieces stick together?

[weeble]

Mark, if you're willing to fund the study, I'll do the work! I honestly don't know EXACTLY what happens at the chemical level, but my own observations make me think the vinegar is interfering with the bonds between the clay particles, rather than reacting with the sodium or calcium. When used in repairs on bone dry clay, the vinegar works better than regular water because the repair is less likely to re-crack as the slip shrinks. Its not perfect, just better than water! Mostly I use a tiny bit of vinegar to soften the two edges, then make slip to stick the pieces together. The vinegar on the surfaces gives you more time to get the pieces in position and stuck together.

I had a batch of home grown clay from my yard that just would NOT settle and it was giving me fits. I mean over a week later it was still totally suspended in the bucket, sand and all, even though I had enough water in there that it was almost milk thick. I really wanted that sand out of there, and somewhere found a reference to vinegar as a flocculant, so I started adding just to see what happened. Sure enough, within minutes of adding about a cup of vinegar to a 5 gallon bucket of muck, the sand settled out and I could pour off the USABLE stuff. A couple days later I had wedgable clay. The stuff worked up wonderfully after that, nice and plastic, great for hand-building, and matured at cone five a very nice brick color. Right now I'm having fits because they're doing construction in the next lot over and they've scraped all the surface soil off revealing a BEAUTIFUL layer of pale gray clay. Its still has sand and small rocks in it, but its got far FAR fewer impurities than the lumps I was finding in the flower bed. I've been plotting a raid, but they've got the place fenced off so maybe not.

[Phylosilicates]

From a chemistry standpoint, don't mix up too much magic water in advance. The sodium silicate reacts with the sodium carbonate and is rendered ...not sodium silicate. It will still have its firing value of a stronger bond, but it won't really have the same characteristics of fresh vs. 8hrs (if you have that long). Sodium silicate will absorb carbon dioxide out of the air fairly quickly and form a glass skim. The gunk in the bottom of the silicate chemical bottle is reacted silicate. This is the same process I (will) use for blow molding. I prepare the two halves of the sand casting mold with sand wetted with silicate, and vent CO2 through the mold. They are instantly hard. My old mentor (Elmo Spriggs) put me onto that one. I haven't used it yet, but the process is described in the metal casting handbook. The reaction path for silicate and CO2 was not included, and more like if I did the numbers, they'd be off. On paper here it looks like a hydrate of silicon carbide but I won't commit to that. Suffice to say, it just goes bad after a while.


Even sodium carbonate, something you'd think would be beyond worry, has a few quirks. It also absorbs carbon dioxide out of the air and converts to sodium bicarbonate. Fortunately the reaction is slow unless the air is humid. This bond is easily broken though... nevermind, not pertinent. To the few who mentioned Egg Keep - yep, old time trick. Dip the eggs in the solution, dry, and you could keep the eggs on the counter for up to a year!

Bottom line is, don't make a whole lot. It goes bad, capped or not.

[rebbylicious]

morah, on 28 February 2013 - 06:54 PM, said:

pattial, on 28 February 2013 - 07:40 PM, said:

morah, on 28 February 2013 - 07:05 PM, said:

Isn't there any way to repair broken pots with ingredients that are readily available in your local drugstore? I have no access to the chemicals you keep mentioning. Thanks

I've had luck using plain old vinegar. My first teacher taught me how to attach handles on cups with it. I still use this method and have great success with it

That sounds more like it. Do you use straight vinegar or mix it with something? Will any type of vinegar do?

I literally used "malt vinegar" that I had in the fridge for fish fry's because that is all I had around. (just yesterday) It worked & I got a random craving for fried foods....

[rebbylicious]

Krebs Pottery, on 29 November 2012 - 02:02 PM, said:

I saw a video a few months ago where the potter painted a thin layer of colored slip and then sodium silicate onto a fresh thrown pot (still on the wheel) and then used a torch to only dry the exterior sodium silicate layer. He then expanded the pot from only the inside which created a beautiful crackle pattern on the outside. I am guessing the video was from Ceramics Arts Daily but it may have been YouTube.

I just saw this too- Hischuin Lin (i might be spelling his first name wrong) He also used a blowdryer in another video. His tutorials are so helpful!