Tushen glaze

Mene ne glaze

Glaze siririn shafi ne na gilashi da ya manne a jikin tukunya. Glazy, rumbun bayanai na tsarin glaze a buɗe, ya kira shi "tsarin gilashi da aka daidaita don ya narke ya manne a kan yumɓu a wasu yanayin zafi". Ana shafa shi a matsayin layin gari, kuma yana narkewa a cikin kiln (murhun gasa tukwane) ya zama shafi mai kama da gilashi wanda ke rufe yumɓun, don haka tukunyar ba ta cika yoyo, ɗaukar tabo ko gogewa ba. A ƙololuwar gasar, abin da ya narke yana kuma yin aiki da yumɓun, sau da yawa yana samar da wani layi a tsakaninsu da ke kulle glaze ɗin a jiki. A kan earthenware glaze yana zama a sama a matsayin layi daban; a kan stoneware yana narkewa ya shiga cikin jikin.

Tsarin glaze yana lissafa kayan aiki, kamar feldspar, whiting da kaolin. A cikin kiln, wani ɓangare na kowanne yana fita a matsayin iskar gas (ruwa ko carbon dioxide), sauran kuma ya zama oxide (ogsaid): haɗin wani sinadari da oxygen, kamar silica (SiO₂) ko calcium oxide (CaO). Gilashin da aka gasa an yi shi ne da oxide, don haka maginan tukwane suna bayyana glaze da su. Kowane oxide yana yin ɗaya daga cikin ayyuka uku.

• Silica (SiO₂) ita ce mai gina gilashi (glass former): ita ke gina gilashin. Silica zalla tana narkewa sama da 1700 °C (3100 °F), zafi da ya fi na kiln ɗin tukwane nesa ba kusa ba, kuma glaze mai yawan silica yawanci ya fi jurewa.
• Flux (mai narkarwa) suna saukar da wurin narkewa zuwa wanda kiln zai iya kaiwa. Alkali, da ake rubutawa R₂O, su ne oxide na sodium, potassium da lithium (Na₂O, K₂O, Li₂O); suna aiki daga cone (mazugi) 06 zuwa sama har zuwa gasa ta tsakiya da ta babban zafi. Alkaline earth, da ake rubutawa RO, su ne oxide na calcium, magnesium, barium da strontium (CaO, MgO, BaO, SrO), tare da zinc oxide (ZnO) a rukuninsu; sun fi aiki daga cone 5 zuwa cone 10. Harafin R yana nufin kowane ƙarfe a cikin rukunin.
• Alumina (Al₂O₃) ita ce mai daidaitawa (stabilizer). Tana ƙarfafa abin da ya narke don ya tsaya a kan bango a tsaye, kuma tana ƙara tauri da juriya. Gargaɗin Glazy: idan alumina ta yi ƙaranci "glaze ɗinku zai iya gudana; idan ta yi yawa za ta iya ƙarfafa abin da ya narke ya zama marar sheƙi". Alumina tana zuwa galibi daga yumɓu da feldspar.

Boron (B₂O₃) yana ɓata iyakar. Masana kimiyya suna lissafa shi a matsayin mai gina gilashi, amma a yanayin zafin ɗakin aikin tukwane yana aiki kamar flux, kuma maginan tukwane suna ɗaukarsa haka. Yana da matuƙar muhimmanci a cone 5–6 kuma ba a buƙatarsa a babban zafi. (An bayyana cone, hanyar da maginan tukwane ke sanya wa gasa suna, a ƙasa.)

Hanya ɗaya ta riƙe shi a zuciya: silica ita ce gilashin, flux suna sa ta narke a zafin da kiln ɗinku zai iya kaiwa, alumina kuma tana sa ta yi kauri don ta tsaya inda kuka sa ta.

Yumɓu, shafe-shafe da gasa biyu

Jikin yumɓu

Jikin yumɓu (clay body) shi ne yumɓun da aka yi tukunya da shi. Akwai manyan iri uku.

• Earthenware: jiki na ƙaramin zafi, kusan cone 06–02, wanda ke zama mai kofofi (porous). Sau da yawa ja ko ruwan ƙasa-ƙasa, yana buƙatar glaze don riƙe ruwa.
• Stoneware: jiki na matsakaici zuwa babban zafi, kusan cone 5–10, wanda ke zama vitreous ko kusan haka.
• Porcelain: jiki fari na babban zafi mai yawan kaolin, sau da yawa haske yana ratsa shi.

Vitreous yana nufin kamar gilashi kuma marar kofofi; vitrification shi ne jiki ya zama haka yayin da ake gasa shi. Maginan tukwane na Birtaniya sau da yawa suna raba su da zafi a maimakon haka: ana gasa stoneware sama da 1200 °C (2192 °F), earthenware ƙasa da shi. Gasa ta tsakiya, cone 5–6, tana faɗawa kaɗan a kowane gefen wannan iyaka.

Shafe-shafe da bushewa

Slip (yumɓu mai ruwa) yumɓu ne da aka narka a cikin ruwa, don zubawa a gyambo, haɗawa ko ado. Engobe shafi ne kamar slip, sau da yawa mai launi, mai ƙarin kayan da ba yumɓu ba. Underglaze ado ne na slip mai launi ko na oxide, wanda yawanci ake rufewa da glaze mai haske (clear).

Kayan da ba a gasa ba shi ne greenware (majiyoyi ba su yarda ba ko kalmar ta ƙunshi duk kayan da ba a gasa ba ko busassun kawai). Yayin da yake bushewa yana zama leather-hard, mai tauri amma da ɗan danshi, lokacin gyara siffa da sa hannaye; sannan bone dry, babu sauran ruwa a cikinsa, yana da matuƙar saurin karyewa kuma a shirye don gasa.

Gasa biyu

Gasa ta farko, mai ƙaramin zafi, ita ce bisque (gasa ta farko; Birtaniya: biscuit), yawanci cone 08–04 (galibi 06–04), kusan 942–1063 °C (1728–1945 °F). Tana barin kaya da ƙarfi amma da kofofi. Digitalfire, shafin bayanai kan glaze, yana ba da shawarar kofofi fiye da 15% gaba ɗaya, don bisque ɗin ya tsotse ruwa daga glaze yayin da ake shafawa. Bisque mai laushi (cone 08–06) ya fi kofofi; bisque mai tauri (sau da yawa cone 04) ya fi ƙarfi amma ba ya karɓar glaze da sauƙi.

Potclays, mai sayar da kaya a Birtaniya, ya bayyana gasar biscuit zuwa kusan 1000 °C (1832 °F), kusan cone 06. Idan muka karanta waɗannan majiyoyi tare, muna ba da shawarar cone 06–04 don bisque na farko: 998–1063 °C (1828–1945 °F) a matsakaicin saurin Orton.

Gasa glaze (glaze firing; maginan tukwane na Birtaniya na iya cewa gasar glost) tana narkar da glaze kuma, ga stoneware, tana kuma nuna yumɓun. Gasa sau ɗaya (once-firing) shi ne shafa glaze a kan kayan da ba a gasa ba a gasa shi sau ɗaya kawai. Digitalfire ya ba da labarin wani wurin samarwa inda kayan da aka shafa wa glaze ba tare da gasa ba suka yi crawling a bakinsu har sai da gasar bisque ta magance shi, don haka ku fara da gasa biyu. Gasa a cikin kiln mai sauƙi yana ba da jadawalin duka biyun.

Cone da aikin zafi

Maginan tukwane suna sanya wa gasa suna da cone: siririn dala na tukwane da ke lanƙwasawa idan ya sami wani adadin zafi da aka ƙayyade. Orton, wanda ke yin su, ya faɗa haka: "Cone ba sa auna zafi kaɗai. Suna auna aikin zafi, haɗaɗɗen tasirin lokaci da zafi."

Aikin zafi (heatwork) shi ne dalilin: glaze, yumɓu da cone duk suna amsa tsawon lokacin da suke cikin zafi da kuma yawan zafin. Gasa a hankali tana lanƙwasa cone a ƙaramin zafi, gasa da sauri kuma a zafi mafi girma. Jadawalin Orton ya nuna cone 6 yana lanƙwasawa a 1185 °C (2165 °F) idan gasar ta ƙare tana hawa 15 °C (27 °F) a kowace awa, a 1222 °C (2232 °F) a 60 °C (108 °F) a kowace awa, kuma a 1243 °C (2269 °F) a 150 °C (270 °F) a kowace awa, saurin da aka auna a cikin 100 °C (180 °F) na ƙarshe. Cone ya kammala idan kansa ya lanƙwasa har 90°, abin da Orton ke kira matsayin ƙarfe 5 na agogo.

Lambobin cone suna tafiya daga 022 zuwa 42. Sifili a gaba yana nuna jerin masu sanyi, inda babbar lamba ta fi sanyi: cone 06 ya fi cone 04 sanyi, kuma cone 01 ya fi cone 1 sanyi.

Ku sanya wa gasarku suna kuma ku tsara ta da cone, ku ɗauki yanayin zafin a matsayin kimanin kawai. Cone mai shaida (witness cone) a kan shiryayye a cikin tukwane, ko fakitin cone guda uku (cone na jagora, na gasa da na tsaro), yana nuna aikin zafin da tukwanenku suka samu da gaske.

Yanayin zafin da aka wallafa ya bambanta. Glazy ya ba da babban zafi, cone 9–11, a matsayin kusan 1280–1310 °C (2336–2390 °F), wanda ya dace da ginshiƙin Orton na sauri, kuma Digitalfire ya ce yawancin kiln suna kaiwa cone 6 a kusan 1204 °C (2200 °F). Shawararmu: ku yi amfani da alƙaluman Orton na matsakaicin sauri, kamar yadda wannan jagora ke yi, ku tsara da cone, ku bar cone mai shaida ya yanke hukunci.

A wajen Arewacin Amurka, masu sayar da kaya sau da yawa suna ba da °C maimakon cone. Hermann Seger ne ya ƙirƙiri cone na zamani, wanda aka fara amfani da shi a Berlin a 1886, kuma Birtaniya ta daɗe tana da nata cone na Staffordshire; bai kamata a ɗauka lambobinsu sun yi daidai da na Orton ba, kuma ba mu sami jadawalin canza su ba. Gasa a cikin kiln mai sauƙi ya yi ƙarin bayani kan cone.

Daga tsarin glaze zuwa UMF

Tsarin batch (batch recipe) yana lissafa kayan aiki da nauyi, yawanci an daidaita su don tushen ya kai 100. Ƙari (additives: masu launi, masu hana haske ratsawa da masu riƙe kaya a cikin ruwa) suna hawa a kan 100 ɗin, yawanci a matsayin kaso na tushen. Don ganin ainihin glaze ɗin, maginan tukwane suna mayar da tsarin zuwa UMF (unity molecular formula) (ko tsarin Seger, saboda Hermann Seger, wanda ya fara amfani da tsarinsa na ginshiƙai uku).

Shafin tsarin glaze na Glazecalc yana yin duk matakai huɗu yayin da kuke rubutu, kuma yana nuna sakamakon a ginshiƙai uku: flux (R₂O da RO) da ke kaiwa 1; masu daidaitawa (R₂O₃: alumina, sau da yawa da boron a nan); da masu gina gilashi (RO₂: silica). "Unity kayan aiki ne na daidaita girma kawai," in ji Glazy: tsarin glaze biyu da aka yi da kayan aiki daban-daban amma da UMF ɗaya "suna kusan yin abu ɗaya bayan an gasa su". Don haka 1 ɗin ma'auni ne na kowa, ba adadin da za ku auna ba. Digitalfire ya ƙara cewa hanyar "ba ta aiki sosai a ƙananan yanayin zafi", inda boron ba flux kawai ba ne, kuma UMF "na kwatantawa ne kuma ya fi kyau a gan su a cikin mahallinsu". Kwatanta yana jera UMF na tsarin glaze biyu oxide bayan oxide.

Rabon silica da alumina

Lamba ɗaya mafi amfani ita ce rabon silica da alumina: silica a raba da alumina. A cikin misalin, 3.70 ÷ 0.41 kusan 9 ne.

Rabon 5–7 ba ya hasashen sheƙi ko rashin sheƙi shi kaɗai: flux, boron da cone duk suna motsa iyakar. Glazy ya ba da daidaiton flux na yau da kullum ga glaze masu daidaito na 0.2 R₂O tare da 0.8 RO, har zuwa 0.3 R₂O tare da 0.7 RO. Ƙarin alkali yana sa abin da ya narke ya fi gudana kuma yana ƙara faɗaɗawarsa saboda zafi, don haka da haɗarin crazing.

LOI

LOI (raguwar nauyi a wuta; loss on ignition) shi ne nauyin da wani kaya ke rasawa a cikin kiln yayin da ruwa, carbon dioxide, abubuwan halitta (organic matter) ko sulfur ke fita a matsayin gas. Glaze da aka gasa ba shi da shi, don haka UMF ba ya ƙunsar sa.

Gas da ke fita bayan glaze ya fara narkewa dole ya yi kumfa ta cikinsa, yana haifar da, a kalmomin Digitalfire, "kumfa, ƙuraje, ƙananan ramuka, crawling". Talc yana ci gaba da fitar da gas har kusan 899 °C (1650 °F). Frit, kayan da aka yi wa calcine (an gasa su tun da farko don korar gas ɗinsu) da canje-canje ga gasar duk suna taimakawa.

Tsofaffin littattafai suna yin wannan lissafin da hannu, da nauyin molecular (molecular weight: nauyin mole ɗaya na kaya ko oxide) da nauyin daidaitawa (equivalent weight: nauyin kayan da ke ba da mole ɗaya na oxide). Bisa lissafinmu, kusan 100 g na whiting yana ba da mole ɗaya, 56 g, na calcium oxide. Na'urar lissafi tana yin duka biyun.

Frit da kayan aiki

Frit

Frit gilashi ne da aka yi a masana'anta: ma'adinai da aka narkar, aka sanyaya cikin ruwa nan take, aka niƙa. Yin frit yana sa kayan da ke narkewa a ruwa kamar borax su daina narkewa, yana kulle oxide masu guba kamar darma (lead, Pb) da barium a cikin gilashi mai daidaito, yana ba da kaya mafi daidaito fiye da ma'adinai ɗanye, kuma yana korar gas, don haka glaze na frit "sun fi rashin lahani sosai" (Digitalfire). Frit kuma suna narkewa da wuri: frit na soda yana aiki a cone 06, yayin da feldspar "yana fara laushi ne kawai a cone 6". Sun fi tsada, suna buƙatar yumɓu don su tsaya a cikin ruwa (misalin Digitalfire shi ne frit 85% da yumɓu 15%), kuma "a ka'ida ba sa narkewa a ruwa, amma a zahiri, suna narkewa".

Frit na Arewacin Amurka ana kiransu da sunan mai yinsu da lamba: Ferro Frit 3134 (Ferro yanzu Vibrantz ne) yana cikin kusan 22% na tsarin glaze na jama'a na Glazy. Tsarin glaze na Birtaniya sun fi ambaton frit na gama-gari, kamar standard borax frit.

Kayan aiki na yau da kullum

Sunaye a yankuna

• Kaolin shi ne china clay a Birtaniya; masu sayar da kaya na Ostiraliya suna sayar da shi a matsayin Eckalite.
• Flint tsohon suna ne na silica a Birtaniya. Masu sayar da kaya na Birtaniya har yanzu suna sayar da calcined flint a matsayin kaya na daban, don haka "flint" a tsarin glaze na Birtaniya mai yiwuwa yana nufin calcined flint, kuma a na Amurka mai yiwuwa niƙaƙƙen quartz. Ana sayar da duka biyun a matsayin tushen silica; ku duba nazarin.
• China stone da Cornish stone (Cornwall stone) kaya ɗaya ne, mai alaƙa da feldspar.
• Whiting calcium carbonate ne; masu sayar da kaya na Jamus suna kiransa Kreide (alli).

Ku auna kaya da oxide da yake bayarwa, ba da sunansa ba. Glazecalc yana aiki haka: kuna iya shigar da nazarin mai sayar muku da kaya a shafin Kaya, kuma Gwada kayan zamani kuma ku kwatanta, Ba da shawarar adadi kuma ku kwatanta da Daidaita da abin da nake da shi duk suna daidaita oxide na bayan gasa, ba sunaye ba.

Kaya ma suna canzawa. Custer feldspar ya ƙare a 2023. Asalin ma'adinar Gerstley Borate ta rufe a kusan 1999–2000; Laguna har yanzu tana sayar da wani kaya da wannan suna, kuma Gillespie Borate shi ne babban madadinsa. Majiyoyi ba su yarda ba ko Gillespie yana maye gurbin Gerstley Borate fam da fam (mai yinsa da Potclays sun ce eh, Digitalfire da wasu sun ce a'a), don haka ku kwatanta su biyun a Glazecalc, sannan ku gwada ƙaramin batch.

Masu launi da masu hana haske ratsawa

Mai launi (colorant) oxide ne ko carbonate na ƙarfe da ke ba glaze launi; stain mai launi ne da aka yi a masana'anta, ya fi daidaito da tsayayye fiye da oxide ɗanye. Masu launi yawanci ƙasa da 5% na tushen ne, da yawa ƙasa da 1%, kuma carbonate yana da kusan rabin ƙarfin oxide ɗin da ya yi daidai da shi.

Adadin cobalt da chrome ana jayayya a kansu da gaske. Glazy ya ce cobalt 0.1% ya isa don shuɗi; Glendale Community College ya ba da ½–2% ko ½–3% gwargwadon yanayin iska a kiln; Birdie Boone, a Pottery Making Illustrated, ta ce 3% ko ƙasa da haka. Ga chrome, Boone ta ce ƙasa da 0.5% kuma Glendale 2–3%. Hanya mafi aminci ita ce fara da kaɗan ku yi line blend: jerin test tile (tayil ɗin gwaji) da ke ƙara kaya ɗaya mataki-mataki daga kaɗan zuwa da yawa.

Glaze na tushe yana canza launin. Tushe mai sheƙi, mai haske yana ba da launi mafi haske; tushe na satin da marar sheƙi, yawanci masu yawan alumina, suna dusashe shi. Magnesium yana tura cobalt zuwa ruwan shunayya, zinc yana mayar da chrome ruwan ƙasa, kuma chrome tare da tin yana ba da ruwan hoda.

Masu hana haske ratsawa

Mai hana haske ratsawa (opacifier) yana sa glaze ya zama opaque (haske ba ya ratsa shi), yana ɓoye yumɓun; glaze transparent (mai haske) yana bari a gan shi.

Dacewar glaze da lahani

Yumɓu da glaze duka suna girma yayin da suke zafi kuma suna raguwa yayin da suke sanyi, kowanne da nasa adadi: faɗaɗawarsa saboda zafi (thermal expansion). Dacewar glaze (glaze fit) ita ce yadda su biyun suka dace. Dacewa mai kyau tana barin glaze an ɗan matse shi da yumɓun; Digitalfire ya ce ɗan matsi yana ƙarfafa kaya, yayin da matsi mai yawa zai iya raunana shi har ma ya tsage shi.

Crazing da shivering

Crazing (ƙananan tsage-tsage) wata raga ce ta ƙananan tsage-tsage. Faɗaɗawar glaze ta fi ta jikin, don haka a lokacin hucewa yana raguwa fiye, ana jan sa kuma yana tsagewa, yawanci saboda yawan sodium da potassium (Na₂O, K₂O). Zai iya kuma bayyana daga baya, a lokacin amfani, bayan sanyaya ba zato akai-akai kamar haɗuwa da ruwa mai sanyi. Idan ana son sa, kamar a raku, ana kiransa crackle. Digitalfire ya ce "a kashi 95% na lokuta maganin shi ne daidaita faɗaɗawar glaze saboda zafi"; hucewa a hankali yana jinkirta crazing ne kawai. Gwajinsa: ku zafafa kayan zuwa kusan 149 °C (300 °F), ku tsoma shi cikin ruwan ƙanƙara, ku shafa alƙalamin felt a kansa don nuna tsage-tsage.

Majiyoyi sun bambanta kan maganin farko. Glazy ya ba da shawarar ƙara silica ko alumina; Digitalfire ya amsa cewa ƙarin silica "yana tsarma KNaO ne kawai" (sodium da potassium); Linda Bloomfield tana ƙara boron ko rage feldspar, kaya ɗaya a lokaci guda. Shawararmu: a na'urar lissafin tsarin glaze, ku musanya wani ɓangare na sodium da potassium da flux masu ƙarancin faɗaɗawa (boron, lithium, magnesium, calcium), ku duba canjin da Kwatanta, ku tabbatar da gwajin ruwan ƙanƙara.

Shivering shi ne akasin haka: faɗaɗawar glaze ta yi ƙasa sosai da ta jikin, don haka an matse shi fiye da kima kuma yana ɓarewa daga baki da gefuna. Digitalfire ya yi gargaɗi cewa ɓawon na iya zama kaifi kamar reza kuma ana iya haɗiye su, kuma Glazy ya kira shivering "ya fi crazing haɗari a kan kayan amfani". Maganin shi ne glaze mai yawan faɗaɗawa ko jiki mai ƙarancin faɗaɗawa.

Mai sheƙi da marar sheƙi

Fuska mai sheƙi (gloss) tana nuna haske kuma tana da santsi, satin yana da sheƙi a dusashe, kuma marar sheƙi (matte) ba ta da haske. Sheƙi yana buƙatar gilashi da ya narke cikakke. Rashin sheƙi zai iya zuwa daga yawan alumina (ƙaramin rabon silica da alumina), daga flux kamar calcium, magnesium, barium ko strontium suna samar da ƙananan ƙwayoyi (crystals) yayin da glaze ke hucewa, ko daga rashin gasa sosai.

Lahani na yau da kullum

Ku canza abu ɗaya a lokaci guda, kuma ku ajiye test tile ɗinku.

Lafiyar abinci

Zubar ƙarfe (leaching) shi ne ƙarfe yana narkewa daga glaze da aka gasa zuwa cikin abinci ko abin sha, kuma glaze zai iya bayyana cikakke amma duk da haka ya yi shi. Gwaje-gwajen doka suna jiƙa abin da aka gasa a cikin ruwan acid kuma suna auna darma (lead, Pb) da cadmium da suka fito.

Babu darma ba ɗaya ba ne da lafiya ga abinci

Dokokin Amurka, EU, Birtaniya da Ostiraliya suna iyakance darma (Pb) da cadmium da abin da aka gasa ke fitarwa, ba abin da glaze ya ƙunsa ba. "Babu darma (lead-free)" yana cire haɗari ɗaya; ba ma'aunin lafiyar abinci ba ne. Wasu oxide ma suna yin zubar ƙarfe: Glazy ya yi gargaɗi cewa glaze masu yawan barium "na iya yin zubar ƙarfe kuma gaba ɗaya ba su da lafiya ga abinci", Digitalfire ya ce copper "zai iya sa glaze ya yi zubar ƙarfe; ku gwada shi", kuma Glazy ba ya sake ba da shawarar glaze na darma (Pb) ga kayan amfani.

Liner glaze glaze ne mai daidaito, yawanci mai haske (clear) ko fari, don fuskokin da ke taɓa abinci. A ganinmu, wanda ba shi da mai launi, barium, darma (Pb) ko lithium, wanda ke narkewa cikakke, ba ya yin crazing kuma yana jurewa, shi ne zaɓi mafi ƙarancin haɗari. Ƙarancin haɗari ba hujja ba ne.

Limit formula (Digitalfire ya fi son target formula) suna ba da kewayon UMF na yau da kullum ga glaze masu daidaito a wani cone: target na cone 6 na Digitalfire sun sa alumina a 0.285–0.64 da silica a 2.4–4.7. Suna jagorantar ku zuwa ga kimiyya mai kyau amma ba su tabbatar da komai ba; Digitalfire yana guje wa kalmar "limit" saboda tana nuna cewa glaze da ke cikin kewayon "suna da aminci ta wata hanya". Kayan aikin Glazecalc na canza tsarin glaze suna faɗa idan sabon ya wuce iyakar da aka ba da shawara, kamar yawan boron a cone 6, da abin da glaze ɗin zai iya yi.

Iyakokin doka sun bambanta daga ƙasa zuwa ƙasa. Jadawalin yana nuna na inda kuke zaune, a raka'o'in dokar da kanta; ku zaɓi wata ƙasa ko yanki don kwatantawa.

A Amurka, kayan tukwane na ado da suka yi kama da ana iya amfani da su don abinci ana ɗaukar su a matsayin kayan abinci sai dai idan suna da lakabin manne da sanarwa ta dindindin da aka ƙera ko aka gasa a ƙasansu, kamar "Not for Food Use. May Poison Food", ko suna da rami ta cikin fuskar abinci. EU ta sa iyakokin darma (Pb) da cadmium a Directive 84/500/EEC, kuma Birtaniya ta riƙe alƙaluman iri ɗaya a cikin nata dokar. Daga 29 Mayu 2026 Netherlands, Belgium da Luxembourg suna ba da izinin darma (Pb) ƙasa da kusan sau 130 zuwa 150, da cadmium ƙasa da kusan sau 15. Ostiraliya ta sa iyakoki ga kayan da ake shigowa da su; ba mu sami iyakar hukuma ga kayan da aka yi a Ostiraliya ko New Zealand ba.

Gwaji

FDA ta ce kayan gwaji na swab na gida na iya nuna darma (Pb) da ke zubowa, amma Ceramics New Zealand ya yi gargaɗi cewa alƙalaman gwaji ba don tukwane aka yi su ba kuma suna nuna akwai darma alhali babu (false positives). Ku ɗauki sakamakon da ya nuna darma (positive) a matsayin dalilin daina amfani da abin, kuma wanda bai nuna ba (negative) a matsayin wanda bai tabbatar da komai ba. Gwajin zubar ƙarfe (leach test) na dakin gwaje-gwaje akan abin da aka gasa (ASTM C738 a Amurka; EN 1388 ko ISO 6486 a Turai) shi ne ainihin amsar.

SG da shafawa

SG

Garin glaze da aka haɗa da ruwa shi ne slurry. SG (specific gravity) ɗinsa shi ne nauyinsa idan aka kwatanta da girma iri ɗaya na ruwa, wanda SG ɗinsa 1.0 ne: idan ya fi girma, gari ya fi yawa a cikin bokiti. Tsofaffin littattafan Birtaniya suna cewa pint weight. Glazy ya kira 1.4–1.5 "kyakkyawan wurin farawa ga yawancin glaze". Don auna shi, ku auna daidai 100 mL na slurry (Glazy ya ba da shawarar sirinji) ku raba da 100: 145 g yana nufin SG 1.45. Hydrometer ba a dogara da su a cikin glaze da ya yi gel, kuma ruwa yana ƙafewa, don haka ku sake dubawa kafin ku shafa glaze.

Abin da ake nufi ya bambanta daga majiya zuwa majiya. Digitalfire ya sa glaze na tsomawa a 1.40–1.50 da glaze na shafawa da burushi na kasuwa a 1.25–1.55, yayin da Potclays ya ba da 1.71–1.81 don burushi da 1.71 don fesawa. Shawararmu: ku tsoma a kusan 1.45 da glaze ɗin ya ɗan yi gel, ku bi lakabin glaze na burushi, ku rubuta abin da ya yi aiki.

Flocculant (Epsom salts, vinegar ko calcium chloride) yana sa slurry ya ɗan yi gel, yana sa shi ya zama thixotropic: yana gudana idan aka juya shi kuma yana daskarewa idan yana tsaye, don "shafin glaze daidai, ba tare da ɗigowa ba". Deflocculant (sodium silicate ko Darvan) yana tsarma shi. Yadda ake haɗa glaze ya yi bayani kan haɗawa da daidaitawa.

Shafa glaze

Ku fara tsaftace ƙura da maiko daga bisque da soso mai ɗan danshi kawai maimakon wanke shi, wanda ke jiƙa shi. Kada ku hura ƙurar da iska mai matsi (compressed air) ko ku share ta busasshe da burushi: hakan yana sa ƙurar silica cikin iska (Haɗawa cikin aminci da iska mai kyau).

• Tsomawa (dipping) "yawanci yana ba da shafi mai kauri daidai" (Robin Hopper). Lokacin tsomawa yana ƙayyade kaurin: Digitalfire ya lura cewa ana yin glaze na tsomawa na kasuwa a kusan 1.4 don tsomawa na daƙiƙa 5 da 1.5 don tsomawa na daƙiƙa 1.
• Glaze na zubawa (pouring) ya kamata ya zama "ɗan sirara fiye da lokacin da ake amfani da shi don tsomawa"; inda zubawa suka haɗu, shafin yana ninkawa kuma zai iya gudana.
• Glaze na burushi (brushing) suna ƙunshe da gum kamar CMC gum, wanda ke taimaka wa glaze ya gudana ya manne, sannan ya ƙone. Yawancinsu suna buƙatar shafi da yawa, sau da yawa biyu ko uku; ku bi lakabin.
• Fesawa (spraying) tana amfani da glaze mafi sirara sosai, da ake shafawa a "shafe-shafe sirara da yawa, ana gina kaurin a hankali".

Shafi mai kauri sosai zai iya yin crawling, blistering ko gudana. Ka'idodin masu sayar da kaya suna tafiya daga kaurin katin banki zuwa na tsabar dime ta Amurka, bisa ƙiyasinmu kusan 1 mm na busasshen glaze; test tile a kauri kaɗan daban-daban su ne binciken da za a dogara da shi. Wax resist a ƙafar tukunya yana korar glaze, don tukunyar ba za ta manne da shiryayye ba, kuma kiln wash, shafi mai jure zafi sau da yawa na kaolin da silica, yana kare shiryayye daga ɗigowa.

Oxidation da reduction

Gas ɗin da ke cikin kiln, yanayin iskarsa (atmosphere), suna canza yadda glaze ke fitowa. Oxidation yana nufin oxygen mai yawa. "Kiln na lantarki iri ɗaya ne da gasar oxidation," in ji Digitalfire, kuma glaze na oxidation yawanci sun fi na reduction haske, musamman a ƙananan yanayin zafi. A oxidation, copper yana ba da kore da turquoise, iron kuma ruwan ƙasa, ruwan ƙasa mai haske da ja. Kiln na lantarki marar isasshen hanyar iska cike da kayan da ke fitar da gas zai iya samun yanayin iska na tsaka-tsaki fiye da yadda aka nufa; hanyar iska (vent) da aka haɗa kai tsaye da kiln tana taimakawa.

Reduction yana takura oxygen da gangan, yawanci a kiln na gas, na itace ko na musamman. Copper yana zama ja, iron kuma yana zama flux mafi ƙarfi kuma yana ba da celadon (shuɗi-kore zuwa toka-kore, daga kusan ½–2% iron) da tenmoku (temmoku: ruwan ƙasa-baƙi, kusan 5–6% iron). Glazy ya ce celadon da copper red "sun dogara da reduction". Yumɓun ma yana canzawa: a wata kwatancen Digitalfire, jikin stoneware ya fito toka a reduction kuma mai ɗan rawaya a oxidation. Silicon carbide a cikin glaze zai iya yin ƙananan wuraren reduction ko a cikin kiln na lantarki. Don reduction daga cone 010 zuwa cone 3, Orton yana ba da shawarar cone ɗinsa marasa iron.

Ku yi tsammanin tsarin glaze da aka rubuta don kiln na gas mai reduction zai fito daban a kiln na lantarki: celadon ko copper red da ya dogara da reduction ba zai yi kama ɗaya ba a oxidation. Ku duba wane yanayin iska aka yi tsarin glaze don shi, ku rubuta naku, tare da cone, a bayanan tsarin glaze a Glazecalc.

Kowane kiln, har da na lantarki, yana fitar da hayaƙi, don haka ku ba shi hanyar iska. Haɗawa cikin aminci da iska mai kyau ya bayyana yadda.

Ƙamus

Ƙari (additive)

Mai launi, mai hana haske ratsawa ko mai riƙe kaya a cikin ruwa da aka ƙara a kan 100 na tsarin glaze.

Alumina (Al₂O₃)

Babbar mai daidaitawa: tana hana gudana kuma tana ƙara tauri. Daga yumɓu da feldspar.

Ball clay

Yumɓu mai laushin gini da ƙarin iron da abubuwan halitta fiye da kaolin.

Tsarin batch (batch recipe)

Kayan aiki na glaze da nauyi, yawanci suna kaiwa 100.

Bentonite

Yumɓu mai laushi sosai da ake ƙarawa a 1–3% don hana glaze kwanciya a ƙasa.

Bisque (Birtaniya: biscuit)

Gasa ta farko, mai ƙaramin zafi, yawanci cone 08–04 (galibi 06–04), tana barin kaya da ƙarfi amma da kofofi.

Boron (B₂O₃)

A ka'ida mai gina gilashi amma ana amfani da shi a matsayin flux; wajibi ne daga cone 06 zuwa cone 6.

CMC gum

Gum na cellulose da ke taimaka wa glaze ya shafu da burushi ya manne; yana ƙonewa.

Mai launi da stain (colorant and stain)

Oxide ko carbonate na ƙarfe da ke ba glaze launi; stain mai launi ne da aka yi a masana'anta, mafi tsayayye.

Cone (mazugi)

Dalar tukwane da aka daidaita wadda ke lanƙwasawa a wani aikin zafi da aka ƙayyade. Cone mai shaida yana nuna abin da tukwane suka samu.

Crawling

Glaze yana janyewa ya zama ƙwalla a lokacin gasa, yana barin yumɓu a fili.

Crazing (ƙananan tsage-tsage)

Ƙananan tsage-tsage a glaze da ke raguwa fiye da jikinsa; crackle idan ana son sa.

Devitrification

Ƙwayoyi (crystals) da ke tsirowa daga gilashin da wuri a lokacin hucewa, inda ba a son su.

Dunting

Tsage-tsage a tukunya daga matsin hucewa ko zafi, sau da yawa a quartz inversion, 573 °C (1063 °F).

Earthenware

Jiki na ƙaramin zafi (kusan cone 06–02) wanda ke zama mai kofofi.

Feldspar

Ma'adini da ke ba da flux na alkali tare da alumina da silica: potash, soda ko nepheline syenite.

Flocculant da deflocculant

Ƙari da ke sa slurry ya yi gel (Epsom salts, vinegar) ko su tsarma shi (sodium silicate, Darvan).

Flux (mai narkarwa)

Oxide da ke saukar da zafin narkewar silica.

Lafiya ga abinci (food safe)

A doka, fitar da darma (lead, Pb) da cadmium ƙasa da iyakoki a gwajin acid. Ba ɗaya ba ne da babu darma.

Frit

Gilashi da aka yi a masana'anta, aka narkar, aka sanyaya nan take aka niƙa, wanda ke sa oxide masu narkewa a ruwa ko masu guba su daina narkewa.

Mai gina gilashi (glass former)

Oxide da ke gina gilashin, yawanci silica.

Glaze

Shafin gilashi da ke narkewa a lokacin gasa don rufewa da ƙawata tukunya.

Gasa glaze (glaze firing; Birtaniya: glost firing)

Gasar da ke narkar da glaze.

Dacewar glaze (glaze fit)

Yadda faɗaɗawar glaze da ta jiki suka dace; dacewa mai kyau tana barin glaze an ɗan matse shi.

Mai sheƙi, satin da marar sheƙi (gloss, satin and matte)

Mai nuna haske da santsi; sheƙi a dusashe; ba haske.

Greenware

Kayan da ba a gasa ba: leather-hard idan yana da tauri amma da danshi, bone dry idan babu sauran ruwa a cikinsa.

Aikin zafi (heatwork)

Haɗaɗɗen tasirin zafi da lokaci a cikin kiln; abin da cone ke auna.

Kaolin (Birtaniya: china clay)

Yumɓu fari zalla da ke ba da alumina da silica; yana riƙe glaze a cikin ruwa. Ostiraliya: Eckalite.

Kiln wash

Shafi mai jure zafi da ke kare shiryayyen kiln daga ɗigowa.

Zubar ƙarfe (leaching)

Ƙarfe yana narkewa daga glaze da aka gasa zuwa cikin abinci ko abin sha.

Limit formula (target formula)

Kewayon UMF na yau da kullum ga glaze masu daidaito a wani cone; jagora, ba tabbaci ba.

Line blend

Gwaje-gwaje da ke ƙara kaya ɗaya mataki-mataki tsakanin adadi biyu. Triaxial blend yana bambanta uku a kan raga.

Liner glaze

Glaze mai daidaito, yawanci mai haske (clear) ko fari, don fuskokin da ke taɓa abinci.

LOI (raguwar nauyi a wuta; loss on ignition)

Nauyin da aka rasa a gasa yayin da ruwa, carbon dioxide, abubuwan halitta ko sulfur suka fita.

Gasa sau ɗaya (once-firing, single firing)

Shafa glaze a kan kayan da ba a gasa ba da gasa su sau ɗaya kawai.

Mai hana haske ratsawa (opacifier)

Kaya, kamar zircon, tin oxide ko titanium dioxide, da ke sa glaze ya zama opaque.

Oxidation da reduction

Gasa da oxygen mai yawa (kiln na lantarki), ko da oxygen a takure (yawanci gas ko itace).

Oxide (ogsaid)

Haɗin wani sinadari da oxygen; nazarin oxide yana lissafa su da kason nauyi.

Pinholing da blistering

Ƙananan ramuka, ko ramuka masu kaifin gefe, inda gas ya fita ta cikin abin da ya narke.

Porcelain

Jiki fari, mai yawan kaolin, na babban zafi, sau da yawa haske yana ratsa shi.

R₂O da RO

Flux na alkali (Na₂O, K₂O, Li₂O) da flux na alkaline earth (CaO, MgO, BaO, SrO, tare da ZnO).

Shivering

Glaze yana ɓarewa daga gefuna saboda an matse shi fiye da kima; haɗari ne a kan kayan amfani.

Silica (SiO₂)

Mai gina gilashi; ana kuma kiranta flint ko quartz.

Rabon silica da alumina (silica to alumina ratio)

Silica a raba da alumina a cikin UMF: mafi girma yana karkata zuwa sheƙi, ƙarami zuwa rashin sheƙi.

Slip da engobe

Yumɓu a cikin ruwa; engobe shafi ne kamar slip mai ƙarin kayan da ba yumɓu ba.

SG (specific gravity)

Nauyin slurry idan aka kwatanta da girma iri ɗaya na ruwa. Tsohon Birtaniya: pint weight.

Mai daidaitawa (stabilizer)

Oxide, galibi alumina, da ke ƙarfafa abin da ya narke kuma yana ƙara juriya.

Stoneware

Jiki na matsakaici zuwa babban zafi (kusan cone 5–10) wanda ke zama vitreous ko kusan haka.

Thixotropy

Gudana idan aka juya, daskarewa zuwa gel mai laushi idan yana tsaye.

Underglaze

Ado na slip mai launi ko na oxide, yawanci a ƙarƙashin glaze mai haske (clear).

UMF (unity molecular formula, tsarin Seger)

Oxide na glaze a matsayin ƙidayar ƙwayoyin halitta (molecules), an daidaita su don flux su kai 1.

Vitrification

Jiki yana zama kamar gilashi kuma marar kofofi a lokacin gasa.

Wax resist

Kakin zuma da ake shafawa inda glaze bai kamata ya je ba, yawanci ƙafar tukunya.

Whiting

Calcium carbonate, babban flux na calcium; yana rasa fiye da 40% na nauyinsa a gasa. Jamusanci: Kreide.

Majiyoyi

• Glazy Help: Glaze
• Glazy Help: Oxides
• Glazy Help: Raw materials
• Glazy Help: Glossary
• Glazy Help: Analyses
• Glazy Help: Firing
• Glazy Help: Defects
• Glazy Help: Specific gravity
• Orton Ceramic Foundation: Pyrometric cone chart, °F (via The Ceramic Shop)
• Digitalfire: Bisque
• Digitalfire: Bentonite
• Digitalfire: Unity molecular formula
• Digitalfire: LOI
• Digitalfire: Frit
• Digitalfire: Limit formula
• Digitalfire: Glaze crazing
• Digitalfire: Glaze shivering
• Digitalfire: Specific gravity
• Digitalfire: Oxidation firing
• Ceramic Arts Network: Common glaze faults and how to correct them (Linda Bloomfield)
• Ceramic Arts Network: An introduction to color (Birdie Boone)
• Ceramic Arts Network: 8 ways to apply glaze (Robin Hopper)
• Glendale Community College: Glaze color
• Potclays: The difference between stoneware and earthenware
• US FDA: Compliance Policy Guide Sec. 545.450, Pottery (ceramics), lead contamination
• EUR-Lex: Council Directive 84/500/EEC of 15 October 1984 on the approximation of the laws of the Member States relating to ceramic articles intended to come into contact with foodstuffs
• eCFR: 21 CFR 109.16, Ornamental and decorative ceramicware