Dennis Bednarek Posted October 14, 2015 Report Share Posted October 14, 2015 While I'm fairly new at slab building I started building some larger objects than my prior projects. Using 1/4 inch thick slabs I had no problem working with objects up to about 5" tall. However my last projects were in the 8" tall range and it seems like the pieces are extremely delicate as green wear. I was hoping on building the next group of objects in the range of 12" to 15" tall . Is there a guid to slab thickness per the heitght of objects? Link to comment Share on other sites More sharing options...
neilestrick Posted October 14, 2015 Report Share Posted October 14, 2015 If it's a decorative object, then thickness doesn't really matter. If it's meant to be picked up an handled, then you want it to be fairly light. 1/4" should work for most pieces, and they will be plenty strong. If they are just too thin to easily work with, try 3/8" thick. Link to comment Share on other sites More sharing options...
Marcia Selsor Posted October 14, 2015 Report Share Posted October 14, 2015 3/8" sounds about right for that size. When I make slabs for bird bath stems and the bowls, I use 1/2-5/8" The thickness needs to increase and the size of the form increases. It also depends on the type of clay and the forming process.And also depends on the structural reinforcement. Marcia Link to comment Share on other sites More sharing options...
Dennis Bednarek Posted October 14, 2015 Author Report Share Posted October 14, 2015 For Clay I'm using Amaco #25 White Art Clay now. However my earlier projects were using AMCO #27 Terra-Cotta Clay. On smaller objects up to 5" I see little difference between these clays. However now that I'm going larger i'm thinking I need to either go thicker or to a different low fire clay. To give you an idea of my projects think of a box which is roughly 4" square at the base but running 8" to 12" tall. These are aquarium ornaments with square holes in them roughly 1 1/2 inches wide and 2" tall. and the surfaces are carved with designs. Yes they will probably be handled somewhat but where i'm seeing the issue is there delicacy after they are air dried and I'm painting underglaze on them and scraping off some areas. I doubt this will be an issue once it is fired, but makes me extremely nervous before hand. Link to comment Share on other sites More sharing options...
Chris Campbell Posted October 15, 2015 Report Share Posted October 15, 2015 Try adding some paper pulp to your clay to give your greenware added strength. Not a high % since you want to carve designs but add a bit and see how it goes. This will also make the forms lighter and easier to handle. Link to comment Share on other sites More sharing options...
PeterH Posted October 15, 2015 Report Share Posted October 15, 2015 i'm seeing the issue is there delicacy after they are air dried and I'm painting underglaze on them and scraping off some areas. At what stage of dryness are you carving? In my limited experience getting the slabs firm -- while still join-able -- before assembly made things much easier. Tile-style drying being best (e.g between plasterboards[uK]/drywall[uS?]). If you are worried about breakages during carving maybe you could do at least some of the carving on the slabs before assembly, when they are fully supported from the back. Assembly of pre-patterned slabs is very doable, although obviously there are issues near the joints. In this video the slabs have an impressed rather than carved pattern on them: ... and there is always shellac-resist (alias water erosion) which can be a gentler technique than carving (but don't let things get too wet). http://tinyurl.com/qgp5eb8 Any chance of a picture of your work, to see the sort of carving you are doing? Link to comment Share on other sites More sharing options...
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