Ceramics and Saltwater.. Advice needed

[Sir Amik]

I'd like to craft some ceramic "rocks" for my marine aquarium. My experience in the ceramics world is a little sparse, having only created a few projects within a 6 month period or so, but I understand the very basics. My question is: will a vitrified stoneware still retain some of its porosity? I'm looking for a surface texture on the end product similar to that of finely porous pumice. Also, I'd prefer the piece(s) to be somewhat lightweight as well. Or Would an earthenware of say, ^06 fired to roughly ^03 be a better option for porosity yet still retain its strength to be able t withstand a marine environment? Thanks in advance.

[weeble]

Do you just want the surface texture? Or does it really have to be porous? The surface texture is easy, you can use a stone such as lava and press it into the surface of a slab, then form the slab, or you could roll in something that will burn out such as course cornmeal or coffee grounds. Or use a groggy clay and wipe down the surface of your piece with a damp sponge, exposing the grog to get a rough surface based on the grog. With either of those you can fire it up and get it vitrified, then not worry about it being sturdy.

 

These are little bonsai pots I made with 'stoney' textures, using different techniques. For your aquarium rocks, you'll probably want more irregular shapes. If you form something out of newspaper somewhat loosely (so it doesn't self destruct as it dries) then you can build over that (make sure you put fairly good size vent holes so you can get all the ash out, or just work on one side) and make the surface as rough as you want. I most often work with 1/4" slabs, but you can work somewhat thicker, up to about half an inch. Too much thicker and you're talking HEAVY!

 

This piece is made of a tan clay, textured with a rock stamp I made then given an iron oxide wash. With marine tank, I'd skip the oxide wash, some critters don't deal well with the metals although iron isn't as bad as others (DEFINITELY STAY AWAY FROM COPPER IF YOU HAVE INVERTS!)

 

 

 

 

Ok, this next one was the same tan clay, with course corn meal rolled into the surface, then a terra sigillata made from a dark brown clay body was used, which really shouldn't affect a marine aquarium. I think I did one layer over the cornmeal before firing, then a second layer after the bisque firing.

 

Other things you can use for texture in a slab that have worked really well are tree lichens or moss and bark. Depending on your clay, carefully removing the surface layer of fine particles to expose grog works too. One of my favorite textures (I can't find pics right now, sorry) is a rock with some very irregular quartz veining that leaves a very nice imprint.

 

Vitrified stoneware normally only retains 1 to 5% absorption, so it won't really be very porous at all, but it will take use in an aquarium nicely. I've used pieces in my freshwater aquariums and the worst damage I've done is dropping them, they've held up fine to the water. Marine aquariums will be a bit harsher, but really if the piece is submerged and not drying with salt in it, it should hold up fine. I'll admit, I've never tried building stuff for marine aquariums, my years taking care of them sort of fell between different stints working with clay! You could decorate your 'rocks' with terra sig, or just let nature take its course. You'll probably get a good crop of 'stuff' pretty quickly if you have some texture! If all that fun stuff can grow on the inside of a glass or acrylic tank, it'll surely grow on clay even if its vitrified!

[Sir Amik]

Weeble, very nice pieces! I really just want the surface texture , the only reason for the porosity was to achieve a more light weight piece. I'm willing to tolerate some added weight however if it means longevity: I don't need this project crumbling a few years down the road. If I'm not mistaken( I'm probably mistaken) a vitrified stoneware will only truly reach vitrification starting around ^6 clays and up? How does stoneware accept brighter colored stains? I was planning on using a sight blue or purple tint.

Further, regarding texture: I have a friend with machine shop with various laser cutters, CNC machines etc. For the texture I was planning on simply routing out my texture of choice via CAD software, then forming the stamp with a casting epoxy. My concern though is that the pre fired texture pattern will warp drastically during the firing process, thus rendering the epoxy stamp futile. My question is: will finely detailed texture patterns warp significantly during a pass through a stoneware fire?

[weeble]

The weight of a piece doesn't change between bisque and vitrified, other than any glaze you add, so I'd personally go with vitrified, its much tougher. Although a piece DOES shrink in the firing process so it might SEEM heavier in the end.

 

Warping is a problem that can be from many sources, without knowing exactly what your technique is like, the shapes you plan to fire, the clay you plan to use, I can't even begin to guess how much problem you'll have with warping. With proper clay choice, handling technique, and reasonable shape choices, I have very little problem with warping on these textured pieces at cone 5. The clay you choose is what determines where vitrification takes place. Groggy clay tends to be less 'warpy.' And you have to realize clay has a 'memory', if you ding around with your slab, manipulating it, it is more likely to warp. The texture in and of itself really isn't going to cause a piece to warp, but the tensions you create in the slab in the process of texturing it by pressing into it, any manipulating the slab, the depth of the texture in the slab, and the way gravity works on it in the firing will cause problems.

 

I'm not sure exactly what you're thinking with the epoxy stamp and warping, but I suspect you're overthinking it. It SOUNDS like you're talking about making a form or mold out of the epoxy then either stamping the clay with it or draping the clay over it, OR maybe routing a piece of clay, firing it then using that as a mold for the epoxy? Afraid I can't address that without a better idea what needs addressing!

 

ETA: Oh, as far as the stain you're talking about, are you planning to add it to the clay body, or put it on the surface? My suggestion there is be very careful, most stains are chemical soups that could cause problems in an aquarium. Stoneware takes stain very nicely, and there is always the option of glazes, but I'd stay with regular commercial food safe non-leaching glazes and clays so the piece doesn't end up slowly leaching toxins into your tank!

[Sir Amik]

Thanks Maryjane and nice vases btw in your link. Digging that Jade green one..

In regards to shapes etc: was planning on some irregular shaped semi "branching" pieces with B-Mix Grog Paper clay.. See any issues with that choice?

 

Yes I was planning on drafting up a pattern on CAD and then routing the pattern into aluminum to cast a stamp with epoxy, and then of course stamp the green piece. My concern is that the pattern will warp significantly to a point beyond recognition. If that's probable then perhaps ill just go with the coffee bean/ grounds approach.

 

Stains: was just going to paint the surface. Any brands you can recommend? Have been contemplating a few from Laguna.

Thanks

 

John

[weeble]

ROFLOL Ok, Laguna doesn't make 'paint' they make GLAZE....They also make stains, but I suspect you really mean glaze. Glaze is not paint! Leave the paint for the walls. If you're planning to glaze the piece, be aware glaze can either enhance detail or cover detail. The green on that vase is one of Laguna's cone 5 glazes, I'll have to look it up to double check but I think its "Fern Mist" Laguna glazes are pretty reliable.

 

On your stamp, my suggestion is find a texture you want to use, a stone, a piece of bark, chunk of lava, anything really. Make a stamp out of clay with the texture (most of mine resemble opened mushrooms with the stem for a handle) then bisque it. The texture itself won't change much after you get it dried, just be careful you don't obscure it with handling. Use the bisqued mushroom to texture your final piece and you'll end up with pretty much exactly the texture you started with. You can also carve a lump of clay directly if you want, although I find natural textures tend to look less artificial. Aluminum, epoxy, things like that STICK to wet clay in a very... um, well, bad way. You'll spend a lot of time cleaning an epoxy stamp and fixing your surface. Bisqued clay pulls just enough moisture out of the surface of the clay slab that it pretty much releases right away, leaving the textured surface very clear. You can also just keep using the same stamp over and over without cleaning a mess up.

 

You're just going to have to do some test runs. The B-mix with grog is a good clay, I've never used it with paper but I've used the cone 5 B-mix in several forms and OTHER paper clays. The paper clay will stay porous because of the voids the paper fibers leave. Depending on the overall look you want, with a branchy coral type shape you're going to have a hard time of it unless you are very careful with your construction. The form is just delicate. Paper clay will make that sort of form easier to get into the bisque firing though. Glazing is going to rely on you getting the piece supported so it doesn't fuse to the shelf, which might mean propping it somehow, or just making a well balanced piece. Check out the glazes that mature at the right cone, look for something that fires food-safe. Laguna, Amaco, Coyote, and many others all make glazes I'd use without worry.

[smastca]

Not sure if it's bad form to put another forum's post on here -apologize in advance if it is

 

Check out the aquarium sculptures in this:

http://davesgarden.com/community/forums/t/1218993/

[Sir Amik]

ROFLOL Ok, Laguna doesn't make 'paint' they make GLAZE....They also make stains, but I suspect you really mean glaze. Glaze is not paint! Leave the paint for the walls. If you're planning to glaze the piece, be aware glaze can either enhance detail or cover detail. The green on that vase is one of Laguna's cone 5 glazes, I'll have to look it up to double check but I think its "Fern Mist" Laguna glazes are pretty reliable.

 

On your stamp, my suggestion is find a texture you want to use, a stone, a piece of bark, chunk of lava, anything really. Make a stamp out of clay with the texture (most of mine resemble opened mushrooms with the stem for a handle) then bisque it. The texture itself won't change much after you get it dried, just be careful you don't obscure it with handling. Use the bisqued mushroom to texture your final piece and you'll end up with pretty much exactly the texture you started with. You can also carve a lump of clay directly if you want, although I find natural textures tend to look less artificial. Aluminum, epoxy, things like that STICK to wet clay in a very... um, well, bad way. You'll spend a lot of time cleaning an epoxy stamp and fixing your surface. Bisqued clay pulls just enough moisture out of the surface of the clay slab that it pretty much releases right away, leaving the textured surface very clear. You can also just keep using the same stamp over and over without cleaning a mess up.

 

You're just going to have to do some test runs. The B-mix with grog is a good clay, I've never used it with paper but I've used the cone 5 B-mix in several forms and OTHER paper clays. The paper clay will stay porous because of the voids the paper fibers leave. Depending on the overall look you want, with a branchy coral type shape you're going to have a hard time of it unless you are very careful with your construction. The form is just delicate. Paper clay will make that sort of form easier to get into the bisque firing though. Glazing is going to rely on you getting the piece supported so it doesn't fuse to the shelf, which might mean propping it somehow, or just making a well balanced piece. Check out the glazes that mature at the right cone, look for something that fires food-safe. Laguna, Amaco, Coyote, and many others all make glazes I'd use without worry.

 

Lol,Yes was referring to Glaze. In effect, you're essentially engaging in the action verb of " painting" a glaze correct? Rest assured I wasn't go to throw some Krylon semi gloss on my piece! My bad for breaking the covenant of the clay terms;)

Interesting take on the clay as a stamp. Makes sense. Ill do a couple test runs with a clay stamp as well as some coffee beans and see what I come up with. ( Also to see how the piece itself holds up!)

 

Thanks for the thoughts, they're appreciated.

 

John

[Sir Amik]

Not sure if it's bad form to put another forum's post on here -apologize in advance if it is

 

Check out the aquarium sculptures in this:

http://davesgarden.com/community/forums/t/1218993/

Smastca,

My aim is for some more traditional organic shapes as opposed to Octopus rocks and various other sea creatures etc, but thanks for the link!

[AtomicAxe]

The only time you need porous products is if there is something that needs a root base like some of the lichens, but the trade off of that is the clay needs to be thicker and thus heavier. Vitrified clay has the benefit of strength while being thin AND not absorbing and holding onto water (and contaminates). Of note, in salt ... metallic stains do react with salt so try to avoid it if possible. Some marine grade paints and enamels will work great with vitreous clay in tanks so include some texture (to help hold the paint) and experiment.

[Sir Amik]

The only time you need porous products is if there is something that needs a root base like some of the lichens, but the trade off of that is the clay needs to be thicker and thus heavier. Vitrified clay has the benefit of strength while being thin AND not absorbing and holding onto water (and contaminates). Of note, in salt ... metallic stains do react with salt so try to avoid it if possible. Some marine grade paints and enamels will work great with vitreous clay in tanks so include some texture (to help hold the paint) and experiment.

 

 

Thanks, the porosity is actually extremely beneficial in saltwater aquaria as it provides more surface area within the actual structure to populate beneficial bacteria, but that's a topic for the fish forums lol. I can live without the porosity of it means a stronger piece. I can't have any crumbling down the road. Ill prob stick with a food safe glaze as the MSDS doesn't appear to contain anything caustic. I may however pay for a lab analysis to be done on a water test run down the road just to be certain. Thanks for the feedback