{"product_id":"cobalt-oxide-fifty-five-pounds-rmcoboxi","title":"Cobalt Oxide","description":"\u003cp\u003e\u003cstrong\u003eThe strongest blue in pottery. Use tiny amounts for deep blues, blacks and blue speckles.\u003c\/strong\u003e\u003c\/p\u003e\n\u003cdiv class=\"rm-testing-statement\" style=\"border:2px solid #8a5a00;border-radius:6px;padding:12px 16px;margin:16px 0;background:#fdf6e3;\"\u003e\u003cp style=\"margin:0;\"\u003e\u003cstrong\u003eYou must test before you use it, at any scale.\u003c\/strong\u003e Raw materials, mined or man-made, are not consistent. Color, strength, particle size and chemistry can change from one bag to the next and from one supplier to another, even when the name on the bag stays the same. Before you use this material in a glaze, slip or clay body of any size, mix a small test batch, fire it on your own clay in your own kiln, and check the results.\u003c\/p\u003e\u003c\/div\u003e\n\u003ch3\u003eWhat it is\u003c\/h3\u003e\n\u003cp\u003eA black powder that fires a strong blue. It's about one and a half times as strong as cobalt carbonate. The grains are coarser, so it can leave blue specks unless it's mixed very well.\u003c\/p\u003e\n\u003ch3\u003eGetting started\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eStart at 0.25 to 0.5% in a clear or white base glaze: a quarter to half a gram per 100 grams of dry glaze. Use a scale that reads to 0.1 gram.\u003c\/li\u003e\n\u003cli\u003eAbout 1% gives deep blue; 2% and up nears navy or blue-black.\u003c\/li\u003e\n\u003cli\u003eSieve the wet glaze through an 80-mesh screen, twice if you see specks.\u003c\/li\u003e\n\u003cli\u003eIf your recipe uses cobalt carbonate, use about 0.67 grams of oxide for every 1 gram of carbonate.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eFor glaze formulators\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eBlack cobalt oxide, Co₃O₄. Releases little gas in firing.\u003c\/li\u003e\n\u003cli\u003e1 part cobalt oxide ≈ 1.5 parts cobalt carbonate.\u003c\/li\u003e\n\u003cli\u003eCoarser than the carbonate. Ball-mill or sieve thoroughly for even color, or leave it coarse on purpose for speckles.\u003c\/li\u003e\n\u003cli\u003eSame base effects as cobalt carbonate: purples in magnesium bases, bright blues in alkaline and zinc bases, teal with chrome.\u003c\/li\u003e\n\u003cli\u003eA key ingredient, with iron, manganese and chrome, in black glazes and stains.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eSafety\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eCobalt compounds may cause cancer if inhaled and can cause skin allergies. Wear a NIOSH-approved respirator (N95 or better) and gloves when handling it dry. Clean up with a wet sponge, not a broom.\u003c\/li\u003e\n\u003cli\u003eFor mugs, bowls and plates, keep cobalt low in a stable, tested base glaze, and have the finished glaze lab-tested before you sell the work.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eSizes \u0026amp; pricing\u003c\/h3\u003e\n\u003ctable style=\"width:100%;max-width:520px;border-collapse:collapse;border:0;margin:0 0 14px;font-variant-numeric:tabular-nums;line-height:1.35;\"\u003e\n\u003cthead\u003e\u003ctr\u003e\n\u003cth style=\"padding:0 0 6px;border:0;border-bottom:2px solid #d9d0c4;background:transparent;font-size:12px;letter-spacing:.06em;text-transform:uppercase;font-weight:600;color:#6b6259;text-align:left;width:40%;\"\u003eSize\u003c\/th\u003e\n\u003cth style=\"padding:0 0 6px;border:0;border-bottom:2px solid #d9d0c4;background:transparent;font-size:12px;letter-spacing:.06em;text-transform:uppercase;font-weight:600;color:#6b6259;text-align:right;padding-left:12px;\"\u003ePrice\u003c\/th\u003e\n\u003cth style=\"padding:0 0 6px;border:0;border-bottom:2px solid #d9d0c4;background:transparent;font-size:12px;letter-spacing:.06em;text-transform:uppercase;font-weight:600;color:#6b6259;text-align:right;padding-left:12px;\"\u003ePer lb\u003c\/th\u003e\n\u003cth style=\"padding:0 0 6px;border:0;border-bottom:2px solid #d9d0c4;background:transparent;font-size:12px;letter-spacing:.06em;text-transform:uppercase;font-weight:600;color:#6b6259;text-align:right;padding-left:12px;\"\u003e\u003c\/th\u003e\n\u003c\/tr\u003e\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:7px 0;border:0;border-bottom:1px solid #e6dfd5;background:transparent;text-align:left;\"\u003e½ lb\u003c\/td\u003e\n\u003ctd style=\"padding:7px 0;border:0;border-bottom:1px solid #e6dfd5;background:transparent;text-align:right;padding-left:12px;\"\u003e$46.40\u003c\/td\u003e\n\u003ctd style=\"padding:7px 0;border:0;border-bottom:1px solid #e6dfd5;background:transparent;text-align:right;padding-left:12px;color:#6b6259;\"\u003e$92.80\u003c\/td\u003e\n\u003ctd style=\"padding:7px 0;border:0;border-bottom:1px solid #e6dfd5;background:transparent;text-align:right;padding-left:12px;\"\u003e\u003ca href=\"\/cart\/add?id=52682143924595\u0026amp;quantity=1\" style=\"color:#2340a8;font-weight:600;font-size:13px;text-decoration:none;white-space:nowrap;\"\u003eAdd to cart\u003c\/a\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:7px 0;border:0;border-bottom:1px solid #e6dfd5;background:transparent;text-align:left;\"\u003e1 lb\u003c\/td\u003e\n\u003ctd style=\"padding:7px 0;border:0;border-bottom:1px solid #e6dfd5;background:transparent;text-align:right;padding-left:12px;\"\u003e$77.50\u003c\/td\u003e\n\u003ctd style=\"padding:7px 0;border:0;border-bottom:1px solid #e6dfd5;background:transparent;text-align:right;padding-left:12px;color:#6b6259;\"\u003e$77.50\u003c\/td\u003e\n\u003ctd style=\"padding:7px 0;border:0;border-bottom:1px solid #e6dfd5;background:transparent;text-align:right;padding-left:12px;\"\u003e\u003ca href=\"\/cart\/add?id=52682143957363\u0026amp;quantity=1\" style=\"color:#2340a8;font-weight:600;font-size:13px;text-decoration:none;white-space:nowrap;\"\u003eAdd to cart\u003c\/a\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:7px 0;border:0;border-bottom:1px solid #e6dfd5;background:transparent;text-align:left;\"\u003e5 lb\u003c\/td\u003e\n\u003ctd style=\"padding:7px 0;border:0;border-bottom:1px solid #e6dfd5;background:transparent;text-align:right;padding-left:12px;\"\u003e$369.00\u003c\/td\u003e\n\u003ctd style=\"padding:7px 0;border:0;border-bottom:1px solid #e6dfd5;background:transparent;text-align:right;padding-left:12px;color:#6b6259;\"\u003e$73.80\u003c\/td\u003e\n\u003ctd style=\"padding:7px 0;border:0;border-bottom:1px solid #e6dfd5;background:transparent;text-align:right;padding-left:12px;\"\u003e\u003ca href=\"\/cart\/add?id=52682143990131\u0026amp;quantity=1\" style=\"color:#2340a8;font-weight:600;font-size:13px;text-decoration:none;white-space:nowrap;\"\u003eAdd to cart\u003c\/a\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:7px 0;border:0;border-bottom:1px solid #e6dfd5;background:transparent;text-align:left;\"\u003e10 lb\u003c\/td\u003e\n\u003ctd style=\"padding:7px 0;border:0;border-bottom:1px solid #e6dfd5;background:transparent;text-align:right;padding-left:12px;\"\u003e$701.50\u003c\/td\u003e\n\u003ctd style=\"padding:7px 0;border:0;border-bottom:1px solid #e6dfd5;background:transparent;text-align:right;padding-left:12px;color:#6b6259;\"\u003e$70.15\u003c\/td\u003e\n\u003ctd style=\"padding:7px 0;border:0;border-bottom:1px solid #e6dfd5;background:transparent;text-align:right;padding-left:12px;\"\u003e\u003ca href=\"\/cart\/add?id=52682144022899\u0026amp;quantity=1\" style=\"color:#2340a8;font-weight:600;font-size:13px;text-decoration:none;white-space:nowrap;\"\u003eAdd to cart\u003c\/a\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:7px 0;border:0;border-bottom:1px solid #e6dfd5;background:transparent;text-align:left;\"\u003e25 lb\u003c\/td\u003e\n\u003ctd style=\"padding:7px 0;border:0;border-bottom:1px solid #e6dfd5;background:transparent;text-align:right;padding-left:12px;\"\u003e$1,662.50\u003c\/td\u003e\n\u003ctd style=\"padding:7px 0;border:0;border-bottom:1px solid #e6dfd5;background:transparent;text-align:right;padding-left:12px;color:#6b6259;\"\u003e$66.50\u003c\/td\u003e\n\u003ctd style=\"padding:7px 0;border:0;border-bottom:1px solid #e6dfd5;background:transparent;text-align:right;padding-left:12px;\"\u003e\u003ca href=\"\/cart\/add?id=52682144055667\u0026amp;quantity=1\" style=\"color:#2340a8;font-weight:600;font-size:13px;text-decoration:none;white-space:nowrap;\"\u003eAdd to cart\u003c\/a\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd style=\"padding:7px 0;border:0;border-bottom:1px solid #e6dfd5;background:transparent;text-align:left;font-weight:700;\"\u003e55 lb bag\u003c\/td\u003e\n\u003ctd style=\"padding:7px 0;border:0;border-bottom:1px solid #e6dfd5;background:transparent;text-align:right;padding-left:12px;font-weight:700;\"\u003e$3,044.50\u003c\/td\u003e\n\u003ctd style=\"padding:7px 0;border:0;border-bottom:1px solid #e6dfd5;background:transparent;text-align:right;padding-left:12px;font-weight:700;\"\u003e$55.35\u003c\/td\u003e\n\u003ctd style=\"padding:7px 0;border:0;border-bottom:1px solid #e6dfd5;background:transparent;text-align:right;padding-left:12px;\"\u003e\u003ca href=\"\/cart\/add?id=52682144088435\u0026amp;quantity=1\" style=\"color:#2340a8;font-weight:600;font-size:13px;text-decoration:none;white-space:nowrap;\"\u003eAdd to cart\u003c\/a\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003cdiv style=\"max-width:520px;margin:0 0 12px;padding:12px 14px;border-radius:8px;background:#eef3ee;border:1px solid #d6e3d7;\"\u003e\n\u003cp style=\"margin:0 0 6px;\"\u003e\u003cstrong\u003eFull bags mix and match.\u003c\/strong\u003e Every full bag in your order, of any raw material, adds up. That total sets the price of every bag. Smaller sizes don't count.\u003c\/p\u003e\n\u003cp style=\"margin:0;\"\u003eThis bag's price stays the same at every level, but it still counts toward your full-bag total.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cp style=\"margin:0;font-size:13px;color:#6b6259;\"\u003ePrices from our October 23, 2026 price list.\u003c\/p\u003e","brand":"Sheffield Pottery","offers":[{"title":"1\/2 Pound","offer_id":52682143924595,"sku":"RMCOBOXI","price":46.4,"currency_code":"USD","in_stock":true},{"title":"1 Pound","offer_id":52682143957363,"sku":"RMCOBOXI","price":77.5,"currency_code":"USD","in_stock":true},{"title":"5 Pounds","offer_id":52682143990131,"sku":"RMCOBOXI-3","price":369.0,"currency_code":"USD","in_stock":true},{"title":"10 Pounds","offer_id":52682144022899,"sku":"RMCOBOXI","price":701.5,"currency_code":"USD","in_stock":true},{"title":"25 Pounds","offer_id":52682144055667,"sku":"RMCOBOXI","price":1662.5,"currency_code":"USD","in_stock":true},{"title":"55 Pounds","offer_id":52682144088435,"sku":"RMCOBOXI","price":3044.5,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0677\/5508\/2050\/files\/oxyde-de-cobalt-132-49018680_39c43be0-6069-4f87-a597-31c378e0d0f3.jpg?v=1791876655","url":"https:\/\/www.sheffield-pottery.live\/products\/cobalt-oxide-fifty-five-pounds-rmcoboxi","provider":"Sheffield Pottery Inc.","version":"1.0","type":"link"}