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susieblue

Has Anyone Actually Made Pavers?

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I am having a small brick patio laid next month. The design is two  intersecting circles of different sizes (one for the table, one for a firepit).  To fill the tangent areas between them I am planning to integrate a few of my own handmade pavers. They won't be really large as I want them to last and am concerned about impact cracking them over time. I live in CT so freezing and thawing is definitely an issue.  I would like some advice on this to make sure it works out well. Here's what I do know: 

  • I need to use a well-grogged mid to high fire clay that has a fixed firing range. It'll be cone 6 since my kiln doesn't go to 10.
  • I need to make these fairly (and evenly) thick but not sure exactly how thick that needs to be...
  • I plan to sand-set these, possibly using a polymer sand set as my morter or I may just let them sit on sand and gravel substrate with soil between to grow moss, creeping thyme or something along those lines. I will likely ask my landscaper to set up the base and edging, if it doesn't add too much to the cost. (He's very excited about the design).
  • I'm not sure if a fully vitrified clay will really need glaze but I want to incorporate color and variety so I plan to use a mix of glazed and unglazed, possibly a few found objects/pebbles/glass blobs, etc. (I will probably use Amaco's Potter's Choice.)

Is there anything else I should keep in mind?

Pre-made, cone 6, moist clay recommendations that are available in the Northeast?  

 

Thanks in advance.

 

-Susan

 

Once completed I will post a picture. :)

 

 

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I think you can get by with ^6. But you will definitely need 3% or less absorption/ vitreous. ( I think 3% is cutoff for freeze damage)

 

You are basically making bricks and or thick tiles.

 

I've never made pavers. I'd say test the thickness. Depending on how large. You may be able to getaway with 3/4 inch thick. My thickest tile I've made was 1/2 inch before firing. Slow dry between drywall. I have seen some literature on brick making. But I think tile technique will suffice

 

Thing is you can always make more of your pavers. Should something fail. Much of the strength issues will depend on how well the are installed!!

 

I'm looking forward to hear what the learned ones will have to say about this....

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I will definitely do the porosity testing after my next round of firings. I don't really want to attach tiles to cement since they will be of varying shapes and sizes and I don't want the limitations of concrete paver sizes and shapes.  Since I am not doing it for a client I can always keep in mind that I can replace them if need be. (I'll be my own guinea pig).

 

Any clay recommendations?  I usually buy my supplies from Sheffield and my clay from a local supplier, Rusty Kiln, who carries the Laguna clays.

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After doing the absorption test, I would place a few of the tiles in your own handy-dandy freezer to see if that freezing has any ill effects on your work pieces. This would also be after you color or glaze them.

I had a friend who brought a 30" tall , brightly glazed statue of a dog back from one of her many trips to Mexico and place it in her backyard near Folsom, California. While the average daytime temp in the winter is around 45 degrees, it does freeze on occasion. She was horrified to see about 1/4 of the glaze on the statue had popped off after the first hard freeze.

It would behoove you to test...

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FYI this was recently posted on Clayart, it seems relevant to sculptures, not certain about pavers.

 

There's excellent information on claybodies for outdoor hard-freeze environments in Val Cushing's handbook. He gets pretty technical in terms of figuring how suitable a particular claybody might be, but the basics make sense. It did surprise me when I found out about this, because initially seemed counterintuitive. You don't want to use a highfire claybody unless it is 0% absorption, which is hard to achieve. The problem with most highfire bodies is that there is still some absorption, and over time the water absorbs, and then in a hard freeze it can't get out and the piece cracks or spalls. That's the same reason it's so dangerous to refire a piece that has been in regular daily use in contact with water. The moisture has impacted into the piece and can't escape in the firing, and the piece can explode with enough force to destroy everything else in the kiln and even the kiln itself. I have seen this happen.

Most of the architectural terracotta decorating the exterior of so many buildings in New England and across the Midwest was fired to low-midrange - around cone 2 or 3. The idea is to have enough porosity to allow the pressure of freezing water to escape, but enough mechanical strength to keep the pressure from fracturing the clay, and the right terracotta body fired to low-midrange does that. Regular lowfire bodies are of course very porous with inadequate mechanical strength, and we've all seen examples of lowfire pots, sculpture, or tiles left outdoors in hard-freeze climates, where the surface starts to spall off and eventually the piece just disintegrates.
- Vince

Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka@dtccom.net

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The freeze/thaw cycle is what really gets them. Water works it's way into hairline cracks or porous areas and then re-freezes. PING... spalled  pavers. I was told that sealing them would prevent this... It doesn't. Mine lasted one winter and I thought I was OK. The next winter I lost three, the winter after that six more.

 

The moral of the story is use only high fired tiles. If there is crack or soft area, water WILL find it's way in... take the word of a New Mexican with a leaky flat roof and a patio of spalled pavers.

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What about making the tile as usual and then setting it into a cement base, like making a stepping stone to protect it from absorbing water?  The studio that I work at has tiles set into poured cement on the porch.  We are in Western Pa, so cold freeze and thaw winters with lots of moisture.  The tiles look as good as the day she laid them.

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Wow. Lots of advice. No total concensus on the type of clay...hmmm. I had not planned to set them in concrete but it seems that's one thing that people seem to agree on. Having a freeze-proof substrate would appear to offer the most dimensionally stable solution. The cone of clay to use will have to be an experiment.

I guess this explains the dirth of online/print info available on the subject. And then there are the glazes. Let the testing begin...

Thanks for all the input, fellow clay lovers. :) Tune in next time for after photos and follow up on my trials and errors.

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The cone of clay to use will have to be an experiment.

 

You need to fire it at cone 5 or above. This is the mid fire lower range. The type of clay is up to you. Just so it matures at cone 5 or above. Low fire clay's don't cut it. Outdoor tiles are usually bedded in Thinset mortar, and then grouted with sanded tile grout. Neither of these things have anything to do with the spalling/cracking problem.

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Most brick is made with terra cotta clay, or a variation thereof. Exterior pavers are 1.5 up to 2.5" thick: used for sand set applications. You cannot duplicate the grain size they use in brick: so you will have to buy some heavily grogged terra cotta: the heavier grained the better. (40-50m) Personally I would use a minimum of 1.5" thickness, because they need the additional strength. I would also be tempted to slightly over fire them: they are flat so I do not see an issue in doing this. If you had a pugger, I would tell you to blend your own..... I would be using frit as part of the flux.

Nerd

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I live in a climate that rarely freezes and not for long periods. Some of or tera cotta flower pots have cracked and spalled due to thaw fees cycles outdoors.

I would stick to higher fired clays

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Mark:

For many years terra cotta was used in 1/2 pavers: and still is. They can be used indoors or out with very little problem. The difference being those pavers are extruded under pressure (compaction) and vases are either thrown or cast. I would not be afraid to use terra cotta that is heavily grogged if it was overfired to ensure a solid body. More preferable would be pugging your own with heavy grog and some frit as flux. The frit would ensure that micro fissures would be filled and not void.

Nerd

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