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  1. Hi ...... Have been working on a porcelain hand built box I now just have to attach the top piece But whilst working the piece has shrunk considerably Not sure how to continue Do I cut the top piece to fit the shrinkage Or leave as is and then sand down Thank you Nicky
  2. Hi, I am a total newbie to ceramics, but my daughter and I are excited to be starting this new adventure together! So please bear with me if my topic is showing such a lack of even the most basic understanding of how things work. We are planning on creating artistic 'flat' ornaments.. We do plan to 'bisque fire' & then 'glaze fire' our ornaments. (You'll probably hear from me again when we get to working with our Kiln!) I have been playing around with creating a few ornaments, and now have created a couple of plaster molds of my ornaments... I poured my slip (premixed & purchased from Dick Blick's) into one of my molds. But, as the slip dried, there was such shrinkage of the slip, that the center of the item somewhat collapses & one even cracked, leaving me with a 'bowled ' back of the ornament when what I really want is flat... The castings are between 1/4" thick to a very max of 1/2" thick with a maximum diameter of 2"-3". I have purchased bisque items where they are that thick (with a flat back), so I assumed one can pour slip that thick.. ?? I'd be so grateful for any guidance such as: 1) Suggestions on informative books or videos to educate myself on the basics of ceramics. Probably a very good step to move forward! I have searched YouTube and not found any useful videos dealing with one-piece molds such as what I'm trying to do.. but would so appreciate a highly recommended 'learning the basics of ceramics" book/course/video. 2) Should I be using a specific type of plaster for my molds - maybe what I used to create my mold is absorbing the moisture too fast? 3) Should I be using a specific type of slip? or is Slip even the right material for what we are trying to do?? 4) What might be an expected shrinkage %? 5) Do you pour the slip in thin layers before each prior layer is dry? 6) Any general suggestions (other than telling me I might not belong in the ceramic world)? :-) We all started somewhere! Thank you in advance. Nancy
  3. While looking into shrinkage rates and cracks and plasticity I found a picture I immediately recognised. This picture exactly matches something I've encountered. I thought maybe it was the result of some 60 mesh silica sand I was trying but now I suspect not. As someone looking for any clue along the way this small tidbit helps a bit. Thanks Tony and anyone else at Digitalfire.
  4. Hi all, I'm new in this forum and would appreciate some wisdom on figuring out shrinkage rates. I'm working with Laguna B-mix Cone 5, which as per Laguna has: Avg. Shrinkage 2±%: 12% Avg. Water Absorption 1± %: 2.3% COE x 10-6: 5.74 (note: no idea what COE is. Do you?) Now, what exactly is this 12% shrinkage? Is it the shrinking after both bisque and glaze firings? (I bisque at cone 06, glaze at cone 5). What is the shrinkage from wet to bone dry then? Does this mean, for example, that if I want the drain hole in the sink I'm trying to build to be a finished size, that is, after glaze firing, to be 3.175 cm (which is 1 1/4", I'll use cm since it's simpler for calculations, being decimal and all...), at WET (plastic) stage the hole will need to measure 3.60 cm, where 3.175 cm is 88% (100% - 12% shrinkage rate) of 3.6 cm? Am I figuring this correctly? Where does the 2.3% water absorption rate come into play? Is that the shrinkage that happens from plastic/wet stage and bone dry? If the posted avg shrinkage rate is 12%, how much of that shrinkage happens after the bisque firing and how much after the glaze firing? What happens if, for example, I need to do a second glaze firing, will it shrink even more? And what happens if that second glaze firing is not at the same temperature as the first glaze firing, let's say it's for decals at cone 012? I need to be really accurate for the pipes and hardware to fit correctly on this sink. I'm confused. I'll thank you in advance for any light you can shed on this for me...
  5. Originally published in February 2019 issue of Ceramics Monthly, pages 66,67, & 68. http://www.ceramicsmonthly.org . Copyright, The American Ceramic Society. Reprinted with permission." techno File section: Clay Body Shopping Nerd
  6. I am wanting to try and make sets of measuring spoons. I figured I would use a manufactured set as size references when creating them, but I am not sure how to account for shrinkage in the kiln. Never having made something that needs to have an exact (or close) size I am wondering if its that big of a deal and something that needs to be taken into account or if I should just say 'whatever, I'm sure they will be close enough'. Anyone have any thoughts, ideas, tips, from experience??
  7. Looking into making my own climbing holds for an indoor climbing wall at home. From what I understand they have been made. I just need to figure out the shrinkage of my clay so that the mounting hole is a standard 3/8" like commercially made resin holds. I vaguely understand the concept of shrinkage calculation. Roll a slab the same thickness as your finished product, mark with a ruler 10cm, fire at temp and then check against the original ruler for % shrinkage. Do I just increase the desired hole size by the % and voila? Or is there something else to it? Thanks for any advice.
  8. I've been trying for months now to make a successful octopus that the tentacles won't break on! I'm starting to think I can't! I'm make the tentacles with clay coils and add details. However, when it starts to dry, the tentacles start to raise up. They don't break...but me trying to readjust them or press them back down breaks them. I feel like an octopus is going to look DUMB with his legs in the air!! So here's what I'm doing right now: I've got his body uncovered (so it will dry out...the tentacles are thinner and always dry out fast) and his legs have been misted with water and have a plastic bag draped across them. For weight to counter the rising tentacles, I've laid a cotton t-shirt on top of that. I keep checking and misting...but this seems like a never ending cycle. How do I keep these legs from dring and raising up?!?!
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