Document zdKw88BjyGdJJ6voRJax84Lv6

Lead Industries Association, Inc.------ m UsdWon Avenue Nn Yort. N. Y. 10017 TeW*>Aone: (lit) 7 0000 August 36, 1971 sobjecti new publicatioh cgAimc WITH LEAD GLAZES Tot Member* of the Uad Industries Association, Inc. i It has baac quite apparent fro recant publicity regarding potential and ~TtjP* lead poisoning problsm* that many hobbylata and art or atudlo pottara lack corract information about load bearing glaiaa. Tha ancloaad booklet, Fact* About Lead ,G1 area for'Art Pottara and Hobbylata,* la aimad at correcting that unfortunata altuatioo. Based almoat In lta antlraty on raarch data devalopad by X1ZAO la cooparation with tha 0.6. Pottara Asaociation, thia booklat will be diatrlbutad widely through craft and profaaaional aaaociatlona, aa wall as through coop* arating hobby glaxa producer* and their distributor*. It la expected that thia booklat will go a long way toward* eliminating tragic and unneceaaary death* du* to ingestion of laad from poorly glared and fired ceremit'food and beverage utensil*. If you wish to have a faw extra copies of this publication, pi ease 1st aa know. JTSiIj* Enclosure Vary truly yours, (Ly .4 jv (J Jerome P. Smith Manager, Advertising 6 Technical Service *v N 3445 i'1 SUMMARY Thru tocommepdatioot and otsemrtiont concern glazts intended far food contact terlocet: 1. Ghnt CHWt of kgiWiMll, <ft i>cMiit{ Ini, trlid Mb k* gather end bteowt glen et high ttwptrotrctt. 2. UaltH |W |leu n pnfb (ontiltk^, apfM net fired. It ere W Mi N lit potter red It tut cnloMr. \ 2 Nt element. tlott et he ctaiittliM, imparti all et lit JtiinMt i> i ptopertlot k glot that feed doet. 4. Altietti ceramic atkriali art *j Milt, |lont art aat eta- pietely iatoJoble. AcMi trill attract itgrtliwll fro* the glata Uclndmg M, if it it ftMti The amooat et IhA that aty ba ex tracted Itta erf grraa ftext tariff with tha cArnica/ compoirtioe. Othar teefen which hata a direct bearing aa tha lend aolobility art: a The retie el iegrodiimtt e Thkkeeael fleee enfEcntree a Time mod kaparatat tl firing a Tha condition ti tha Ut etmetfhere 2 It will ha erident haa tha tart that glexot far tu aa food caatact Inrfocel thoold aat ha combined. Handing of hfitmt floret triM dntech tha "balance al ingredienti." end nttiling waaU ha a tew krjr before ate. 4. It it often implied that femoral of lead wiB aab tha gloxa non toxic. Koweeer, (end-free gloxat may contain othar potentially toxic i biary metah; mod tatting thoold ha done to determine Mobility lar theta at watL 7. Cogger thoald aat ha alM, aithar et a ttoia or attid addition, to any load ghrte iataodtd for food contact tarfecet. Kegordlete of haw it it added, cogger will increcta tha lood ratoeM of tha (lata. 2 taw bad compoondt thoold not ba atad to awha flout far food terrier otentik. Only 'few Mobility' fritl thoald ha atad hicaolt they ora innch eater. f. Gloxet ott ha refuted H any chooget era mode ia formelotioa, handling, offlicetiea or firing. 10. Pertont fgrMalotiaf gloxet for tobfewara thoald obteia and rood tha 'ILZtO MonnoI, Lead Gloxet for Dinnerwaro.' 11. Whan wore it grodoced on a rootiae befit for food terrier, "textoa tatting' of grodoctioa itemI thoald ba dona fragrantly. 12 Kilnt thoold ba ogerotad order hoodt rantad to tha otnolfhere. II. Scrogolootly hygienic grocodorat thoold ba obtarrod ia tha ceramic worhihog no tmohing, noting or drinking. Erery Cora thoald ha exererted to eaoid any pottible trantfor of toxic motarioh front bondt and clothing to tha noeth. i vi 2* t i -ft i ? rr i FOREWORD The activities of the non-profes sional engaged in the production of glazed ceramic ware can be sep arated into one of two broad cate gories: (1) Art Pottery and. (2) Hobby Pottery. The art potter will be considered here at one who cre ates his own ware for profit or pleasure, and who most frequently compounds his own glazes. He usually does his own firing as well. In preparing glazes, the art potter can proceed in one of two ways: purchase frits to make his glaze; or start with the various compounds In powder form and combine them In the proper amounts. On the other hand, the hobbyist It one who does not mbc glazes, but purchases them packaged or readymade for application to ware. Nearly all of these packaged glazes arc already fritted. Frequently, the hobbyist may not even do hit own firing, but rather, may return his ware to hobby or art center to have it fired. Because this booklet deals with two groups whose knowledge of the subject at band may be widely di vergent, tome of the Information is elementary. Much of the mate rial here is based on substantia] re search jointly sponsored by the In ternational Lead Zinc Research Or ganization. Inc., and the United States Potters Association.' Some details covered are of vital impor tance which cannot be overesaphasized. We have outlined the safe means for the non-professional to handle and apply lead containing glazes. The objective is to provide informa tion which will assist the art potter and hobbyist in producing a safe finished product--particularly at relates to glazed ceramic items in tended for food and beverage star. There is. u* well, background infor mation on some of the materials with which he is working. Jerome F. Smith Manager, Technical Service Lead Industries Association, Inc. July. 1071 i Vr i; 3 4 1 i[ cc i? s THE CERAMIC GLAZE IS IT A PAINT? Let'* begin by dispelling one popular mlaconceptlon: A ceramic glaze la iu>( a paint. Once the glaze baa been ap plied and fused Into a glassy coat ing. it I* much more chemically re sistant and ha* far greater beat and light stability than any paint could have. Perhaps some confusion results because the glaze is usually ap plied--prior to fusion--by dipping, spraying or brushing, much as a paint But the similarity ends there. No normal paint could withstand the extremely high firing tempera ture necessary to fuse the glaze into a glass. WHAT IS m A ceramic glaze is a thin glassy coating, generally containing silica, which is applied and fused onto a dayware body. After fusion, or firing In the pot ter's kiln, the glaze closely resem bles a pane of glass. It is continu ous. impervious and almost com pletely insoluble when properly for mulated. applied and fired. OF WHAT IS rr COMPOSED? A ceramic glaze might be viewed, in a simple analogy, as a group of minerals or rock components which have been fused in a high tempera, tuie kiln--much the same as Na ture produces molten lava in an erupting volcano and sometimes coats the earth with its glassy sub stance. A major difference, though, between volcanic lava and man made glazes is that, with the latter, a flux is generally used. A flux Is a material that, at high tempera tures, reacts with and helps dis solve all of the glaze components to form a glass. Lead oxide is good example of a flux. It ia an active solvent. In addition to its fluxing action, lead also lower* the glazing temperature.1 Betides lead and silica, glaze* often are formulated with varying amounts of other dements. Any of the following dements might be found in an art or bobby glare for mulation : antimony, barium, bo ron, cadmium, calcium, cobalt, copper, fluorine, lithium, manga nese, sodium, potassium, stron tium, uranium, zinc and zirconium. It is evident from the foregoing list that glaze chemistry can be ex tremely complex. It l further com plicated by the fact that we are dealing with reactions (both within the glaze, and between the glaze and body) that occur at extremely Q high temperature*. IS THE GLAZE SOLUBLE? His torians, geologists, and other stu dents of the past have established that nothing in the world is perma nent. And even though ceramic materials are among the roost per manent. durability can only be judged by comparing one object against another. Thus one glaze coating may change or dissolve less quickly than another, but neither is totally intohible. This is important to keep in mind when considering the question of glaze solubility. HOW IS GLAZE SOLUBILITY MEASURED? it hss become stan dard practice In the US. dinnerware industry to measure the solu bility of a fired glaze by determin ing its acid resistance. More specifi cally, what it determined Is the ability of a given concentration of acid to extract glaze ingredients wia ' rr "' .....; ' ' I' -# - i- from a umplc under rigid teat coo ditlons. I( U possible, using Ikes* p tests, to determine the amount of lead, cadmium, copper, barium, or other potentially toxic heavy metals that leach from a glaze. If the glaze has been properly formulated, applied and fired, the quantity of any of these is very small. For lead, it is less than seven parts per million parts of solution --an amount scarcely measurable with accuracy less than 10 years ago. Normally, these extraction tests use an organic add similar to vinegar. The best current test is that de veloped by the United Stales Food and Drug Administration. Division of Compliance Programs, Bureau of Foods. This method was orig inally published as FDA Laboratory Information Bulletin No. 054, and U produced in the Appendix. The FDA test it used to verify and enforce product safety, and has gained universal application in the U.S. It has replaced the older ASTM test. All glazed ceramic food service utensils manufactured in the U.S. must meet the FDA lead release guideline of less than 7 neicroqranu of lead per milliliter of leaching solution when analyzed by the FDA method. WHY USE LEAD IN GLAZES? Lead oxide, chemically PbO, is a valuable component of many glasses and glazes. Because of its essential usefulness, it has received wide attention from ceramic re searchers since the 18th century. For example, over three hundred separate articles on this subject are referenced in one publication.' Some of the more important characteristics of glazes, derived from their lead oxide content, in dude: 1. Low Melting Range. Lead oxide is one of the classic glass network modifiers. Its strong fiuxing action permits tbs formulation of durable (highly add resistant) glazes that mature at relatively low er temperatures than tbdr leadless counterparts. 1. Wide Softening Range. Lead oxide Increases glaze fluidity (reduces Its viscosity) dur ing firing, and in addition, extendi this property over a wider firing range. Because of the greater margin of safety Imparted by lead un der variable firing conditions, leaded glazes are more fool proof. 3. Low Surface Tension. Low surface tension is the prop erty which contributes to the ability of lead glazes to heal over blisters, drying cracks, and other defects. Coupled with the wide softening range of lead glazes, it ac counts for their superior ma turing qualities. 4. High Index of Refraction. Brilliant glaze surfaces are attained, due to the high in dex of refraction imparted by PbO. 5. Resistance to Deiitrification. The presence of PbO In the glaze reduces tendencies towards undesirable surface crystallization, or devitrifica tion. of the glaze. 6. Color Compatibility. Lead is beneficial to most coloring oxides used in art glazes. WHAT IS LEAD RELEASE? As was pointed out earlier, all glazes are at least slightly soluble In acid. However, research by the Interna tional Lead Zinc Research Organi zation and the U.S. Potters Associ ation has shown that certain proc essing variables within the formu lation. application and firing oper ations have major Influence on the resultant add resistance, and In the absence of proper control, can t- wmmmt 4 Kj'- ' t; 1 s:-' a Er- t *j ;i i * *. *i i i- I > r > 4 r ** 4 (ready tncreaae the solubility ( ex tract*btllty) of lead and other besvy metal* from the glaze. It 1* theae high aolubilJty glazes that are cauae for concern. CAN LEAD RELEASE BE A PROBLEM Ye*. Certain poorly dcilgned glaze*--known to be low In add rcsitunce, even when prop erly fired--tbould not be used on pottery Intended for food and bev erage aervice. Large amount* of lead or other toxic tubttance* could be ingested by the user. Tbe lame problem could develop tf a glaze were underfired. While much lea* of a problem for well designed glazes, underfiring can emphat ically increase the lead release from poorly formulated glazes--partic ularly those low firing glaze* that mature in the cone 07-01 range. Several other factors, which will be mentioned later, such at failure to fully frit the glaze, presence of cop per oxide, application thickness, etc., can noticeably affect lead re lease One point worth emphasis is, that the local percentage of lead in an add resistant lead glaze has am particular bearing on its lead re lease--rather it is tbe ratio of in gredients. the time and tempera ture of firing, etc., mentioned above that determine lead extractibfllty. WHY NOT USE A SUBSTITUTE FOR LEAD? There have been many and extensive Investigations *A during the past fifty years aimed at V developing a satisfactory substitute for lead in glaze* for the dinnerware industry. Many leadless glaze formulas have been developed by making substantial increases in the quantities of alkali and boron ox ides in the glaze batch. These better reproduce the low fusion proper ties found In leaded glazes than tbe remaining standard glaze in gredient*. but at tbe same time fall far short with respect to solubility and toxicity, aa well a* affecting undergiaze colors, and crazing. Other fluxes have also been studied an similarly found wanting., e g. Utbla, strontia. baria and fluorine, aa in a very significant research sponsored by the United State* Pot ters Association.* In tbe final analy sis, there is no dement that wifi, by itself, or in combination, impart ' all of the desirable properties to a glaze that lead will--and do to JBk with reasonable economy and com- wP piece safety when properly handled. When correctly formulated, applied and fired, lead fluxed glaze* are among the safest and most add re sistant of all. CONTROL OF LEAD RELEASE HOW CAN LEAD RELEASE cup*, mugs or other food and bev FROM FOOD CONTACT SUR erage utensil*. FACES BE CONTROLLED? *CootreT of lead rtleue U esaential If the hobbyist's or art potter's end ptoduct is to present no danger to the public. It can be achieved by following one or more of these procedure*: The second method (2) for coo trolling lead release--lie., the use of proper glaze* and proper firing --It much more complicated. While we do not yet have all tbs answers, some of the potential diffi culties are discussed snd their solu 1. Design and fire Purdy dec tions indicated in the following sec r orative piece* only i. Use only highly acid resistant tion. Particulalry as regards lowfire (hobby-type, cone 07-02 ) glazes, lead glazes for food and bev there Is still much to be learned on erage contact surface*, and the subject of glaze solubility snd fire property. proper firing. 3. Use Iradlest glatri for food and beverage surfaces. Much of the more definitive glaze research work done up to now has While all these solutions are addressed itself mainly to the high practical, the first (1) is by far the er fired (cones 4 & 5) dinnerware most easily achieved. In this case, 9 tf the art potter Is concerned about glazes. Even though a number of Important factors involving bobby- the safety of his products, or if he type glazes were investigated. It it at all uncertain of hit ability to has become apparent that the low control their end use, then he fire glazes present additional risks should make any such items use with respect to lead release unless y less for foods and beverages by particular care and Judgment are the simple expedient of drilling one exercised in their use. Research is or more boles up the sides or in now in progress that is expected ip their bottoms. Pitchers, mugs, shed more light on the low temper vase*, or other potential beverage ature glazes. containers can thus be rendered Regarding procedure (3). sug unfit far use. No one will drink or gesting that leadless glazes be used pour out of a 'dribbler.* Another for food and beverage utensils, technique for averting unintention much of the fine stoneware manu al food use is to fire a warning label factured by art craft studio* today into the glaze. Such a label as "This either it not glazed, or is glazed container is not safe for food with a leadless mix--Including stuffs* should suffice. For teachers even those based on salt Stoneware and instructors in art pottery, the is fired at a higher temperature, procedure* mentioned above should usually above cone 6. Art potters be stressed at the beginning and and hobbyists who would employ repeated throughout any course in this technique to avoid use of lead art pottery. In this context, it is should therefore be certain the tem also highly desirable that begin perature* required are not beyond ning student* be discouraged alto the firing capabilities of their kilns. gether from designing and firing As for low temperature leadless i -.'3&K t Wi f U W;, - I I t-.-i-r"-'*-,V glazes, U It (till not known whether these tre safe for food contact sur faces. Much additional develop ment work will have to be done be fore It can be stated with assurance that the heavy metal solubility of such glazes will provide an ade quate degree of safety for either the art potter or the consumer. WHAT PROCESSING VARI ABLES INFLUENCE LEAD RE LEASE? There are several vari ables in low temperature art or bobby glazing whereby a problem on food vessels can occur. First, since the firing temperature (beat energy input) is lower than for the high firing glazes, the constituents of low temperature glazes are not as likely to fully react with one another and with the body--some times with the result that a good, add resistant glaze is not formed. For the hobbyist, the solution to this problem is, on food surfaces, to use only glazes that give a low lead release. Such glazes should re lease lxss than seven parts per million when tested by the FDA lest. The hobbyist should carefully check the label on each packaged glaze container and follow all in structions to the lettfT. NO GLAZE SHOULD EVER BE USED BY THE HOBBYIST FOR FOOD CONTACT SURFACES UNLESS THE MANUFACTUR ERS LABEL STATES THAT THE GLAZE IS APPROVED FOR SUCH USE WHEN FIRED ACCORDING TO THE IN STRUCTIONS.' More will be said later concerning the art potter who makes his own glaze. A b of bobby (Uw auppHcrt who an members of the United Stetee Potters AaaocUtioa "Ceramic Dinner*are Sur veillance Profram" appear* in the Ap pendix. All of theee euppbert have looted and laktlad tbatr (law. Regarding other variables that can increase the lead release from a low temperature glaze, copper ox- ( We (CuO) is moat to be avoided. Whether the addition la made di rectly or as a stain component la of no consequence; under no condi tion should copper oxide be added to a trad glaze intended for food surfaces. Regardless of the can used In processing and firing, re search has shown that the addition of copper to a lead glaze will pro duce an uncontrollable--and there fore potentially hazardous--in crease in the lead release. Firing time Is another factor that affects lead release. This la espe cially important where low temper ature or art-type glazes are being used. Such glazes customarily call for less beat input than the com mercial dinnerware glaze. It is very Important for the hobbyist and art potter to always use pyrosnetrlc cones--never to fire by Umc alone. TAMS I ^ STANDARD mtOMITOC CONS tee UieA* 07 1803'T 984*C 06 1830 999 OS 1915 1044 04 1940 1060 03 3014 1101 03 3044 1130 9apa '--* eevA eUKl W>**T t4rl*|t OVt") on ** m at met nzz*a** tw at*w The proper use of cones wifi insure that correct time and temperature of firing baa been achieved. Another processing step that as sumes added importance in low fire glazing it thickneu of glaze appli cation. Marquis' hat shown that a thin glaze can, during firing, react with and dissolve body constitu ents. This is desirable because in variably these new ingredients mi-1 '"'V v"'r;T V'i -i ' f' t- TWTT grate throughout the glaze network, strengthen it, and make the glare | more add retiitant. Conversely, with a heavier application (above 3 mill), these dissolved body con stituents may not penetrate the entire glaze, and--if the glaze is not of an Inherently add resistant type--body dissolution will not then provide the needed materials to develop low lead release. The point is then, that while cer tain marginal glazes (with respect to lead release) may have been used on food service utensils in the past, this practice is risky and should not be continued. Certainly, aa Marquis observed: . . (these) glazes should not be used for dinncrwire or food containers unless the relevant product parameters are controlled.* Frequent testing for lead release is mandatory bith suck glazes. To put it another way. It is far more practical and reliable to arcin with a highly add resis tant lead glaze or frit composition in order to Insure the safety of the fired glaze. WHAT ABOUT THE POTTO WHO MAKES HIS OWN GLAZE1 A good deal of the art or studio potter's success In firing add re sistant lead glazes will depend upon his kiln and hit willingness to avoid heretofore popular, 'cook book* formulation*--at least for food and beverage surfaces. Over the years, literally thou sands of glaze formulation* have been offered In publications aimed at the studio potter. If these tvere used on food utensils, feu; would pass current FDA limits for lead, cadmium, or other heavy metal re lease. What then, should be done? We are printing herewith the em pirical and weight percent formu las of several cone 06 glazes which have been developed and tested, and which consistently gave a lead release of less than 7 parts per mil lion (ppm)--even when fired in a static atmosphere electric kiln. If any other glazes are to be used, they must be tested before they can be considered safe for food and beverage applications. TAM! 8 El CONE 06 ACID 8ESISTAMT OOZES *ti (m M% Mi md W% KmM Empirical Formula of daze r. . K*jO CaO 1*0 rfco no, T-Ol i 0.03 0.06 ____ 0.89 0.27 0.15 2.58 0.01 a 0.10 0.14 ____ 0.76 037 032 2.69 0.02 f !" j a 0.05 0.07 0.22 0.72 037 034 238 0.01 'I 4 0.14 031 0.63 038 0.49 2.80 0.03 Y"' i S 0.10 0.13 0.14 0.62 037 0.36 235 0.02 '* * 0.16 0.20 0.08 0.56 0.27 031 2.78 0.03 Vf Weight Per Cent Formula of Glaze f;. 1 0.71 0.93 -- 49.53 6.96 2.71 38.83 035 a Ml 1.92 -- 42.69 7.03 535 4037 032 a 0.81 0.96 5.78 4031 7.11 4.22 40.34 036 % 4 2.49 2.94 35.71 7.n 834 4231 0.80 i.64 1.96 3.89 36.47 7.13 633 41.74 0.53 * 2.SI 2.97 1.97 3231 7.14 9.12 43.17 0.81 i1 No** Wtv4t *4 |Uin M (W, Horn 4, I 4 ifv c4f ttf 1 t 1 <8l>lf tfefht yoFW-W> taM. >8nM<i > rililT*ftin* 'iiiiliflfr , If the potter 1< using a smaller ware fired hi small "static atmo electric kiln to fire food service ves sphere* kilns. Such deposits Cannot sels, greet cure should be exerdied, chemically recombine with the 1 especially with glues other than glaze, and great variation In the those listed above, to assure that lead release will frequently occur sufficient ventilation exists at all under these conditions. This Is true :* times within the kiln. This will even If It has been shown that the help to prevent rcdepotltlon of vo glaze would otherwise show lead 't latilized lead on the surface of the release of less than 7 ppm when ware. Recent findings have Indi fired In a well ventilated kiln. cated that a distinct "skin effect" or (These are the "marginal" glazes surface layer of lead can occur on referred to earlier.) a THE FRITTED GLAZE Nearly 35 yean ago, J. H. Koe nig* pointed out that the Introduc tion of lead to a dlnnerware glaze In the form of a properly consti tuted. acid resistant frit provided, "... a vast improvement in the re duction of the industrial hazard, as all industrial toxicologists agreed." Now, talking about consumer haz ard It has become even more obvi ous. indeed imperative, that the lead compounds in places used for food surfaces must be rendered in soluble. Lead compounds can best be made Insoluble through fritting, which is the core of this statement. WHAT ARE FRITS7 Frita are glaze components which have been fused or melted In a separate fur nace before incorporation in the glaze. Either the entire glaze or various components may be fritted. These pre-treated glass particles are then reduced to powder form and applied to the pottery for firing. One of the primary objectives In pre-melting (fritting) glaze mate rials is to make them leu soluble-- both before application and after firing. In addition, properly de signed lead frits and fritted glaze* eliminate--or greatly minimize-- lead volatility under gloat kiln con dition*. A note of caution, however. More frits are soluble than It commonly understood. Many commercial frita now supplied and used for glaze formulation are very soluble, and could not resist even dilute acid attack (for Instance, in stomach adds). Merely melting the glaze components to form a frit docs not Insure that It has been rendered in soluble. Just as with the fired glaze, the add resistance of a frit la closely related to Us chemical com position. This complicates the prob lem facing the art potter who wishes to make a "safe" glaze. Un less he is extremely lucky--or un less be uses a fritted glaze known to be add resistant, hit product can become a hazard to an unsus pecting consumer. Three lead frit formulations shown by Marquis' to be highly add resistant are listed below in Table III. Even these frits can be used to formulate an unsafe or highly soluble glaze unless the art potter carefully avoids overloading 3-rsr. -v*^ - the glaze with additional raw lead, or bora* or even copper stains. I More on this subject may be found In the publication "Lead Glazes for Dinnerware,"1 available through Lead Industries Association, Inc. TABU M low Solubility lead Frits Mo! Ur FormuU M --Vit tttka 1. 1.0 2. IO 3. Id) 0.03 0.11 0.25 1.94 2.16 1.92 It** S'***, 'Wl'M. --"**% Raw Lead Claxet. Instead of malting a glaze from lead contain ing frits, U la quite possible to be gin with "raw lead* compounds. When properly formulated, such "raw lead* glazes will Are out to have excellent add resistance. It should be emphasized that glazes made front such "raw lead* com pounds unless perfectly balanced, can be extremely dangerous If ap plied to food service vessels. Some people fed that the use of "raw lead* resulta In a better glaze Sa lih. This is not the case. A fully fritted glaze will produce a finish every bit at good at if "raw lead* had been used. And the equivalent fritted glaze win mature at a kmsr temperature at well. Additionally, "raw lead* glazes are a hazard to the art potter himself. The use cf fritted glazes is the best practice by which the art potter can be assured of low lead release from his prod uct and safety for himself. s HEALTH AND SAFETY THE IMPORTANCE OF GOOD HOUSEKEEPING. ThU section should probably have come first In stead of last. In any event, the ne cessity for good housekeeping can not be over emphasized. Every type of lead product can be safely handled--If It Is handled with suitable care and the proper equipment as In industry. The same long-established hygienic control procedures apply to lead as to allies, barium, beryllium, cad mium, etc. Oust of any kind in the ceramic workshop is likely to be a health hazard. All operations which disperse dust and fumes should be controlled by forced exhaust ven tilation. Fortunately, bobby glazes come packaged In containers of various sizes and no particular handling problem with regard to dust is likely to occur. For the art potter, however, care in mixing and grind ing should be exercised to avoid spills. In addition, when mixing batches of dry materials, respira tory protective equipment should be used--and only respirators ap proved by the U.S. Bureau of Mines* for toxic dusts. Any other type will roost likely be Ineffective. "Raw lead* compounds should not be used by the art potter for ap plication to food and beverage con tainera. However, If such materials are being used in the glazing of non-food ware, all spills should be Immediately damp sponged, and if any dust should appear, It should be vacuumed thoroughly. Shelves * ^w* \i - \ tnd flat turface* should be mopped to lead fume*. In addition, the kiln regularly and meticulously. should be fitted with a hood ex- Spraying of glaze* should be hauttlng to the outdoors. This is wSr done only In a well ventilated especially true for schools and craft booth, exhausted to the out-of- clubs where whole batteries of doors--and not in the vicinity of kilns may be in operation simulta children. On the subject of chil neously. dren, all glaze materials should be Personal hygiene is an elemental stored only in locked cabinets out part of safe bobby glazing. All of their reach. Young children craftas must be scrupulous about should never be permitted to play washing hands, and fake extreme In the ceramic workshop area. care to avoid transferring lead from Young learners should always be the hands to the mouth--THIS supervised by a responsible person MEANS NO EATING, DRINKING to avoid bums, spills and other un OR SMOKING IN THE CERAMIC desirable accidents Little children WORKSHOP AREA. If glove* are have even been known to drink the not worn when glazes are being contents of epen bottles and jar* in dipped or pound, fingernail* and the workshop. hands must be thoroughly scrubbed As we noted earlier, during glaze (use fingernail brush) upon finish firing, lead wiO volatilize from the ing. A protective change of cloth glaze and permeate the atmosphere ing. or a long smock should be within the kiln. Depending upon worn in the workshop and never the size of the kiln, and the quan worn elsewhere in the home, espe tity of ware being fired, the atmo cially where toddlers may come in sphere around the kiln (assuming contact with the clothing. the kiln is properly ventilated) can In summary, observance of iH constitute a very real health haz the foregoing precautions will per- wr ard. It therefore follows that the mlt the hobbyist or art porter the kiln should not be located in the broadest possible enjoyment of his kitchen, den. children's playroom pursuit while at the same time pro or any other are* where children or viding safety for himself, hi* fam adults may unwittingly be exposed ily and those who use his products. ? 10 L > f \ l J t: I V, - ffc. 1 .* METHOD FOR DETERMINATION OF LEAD EXTRACTED FROM GLAZED POTTERY () Alvmk sbts iptlsn spsthswfea Perkin-Pmer Model )03 or #qvivilMf4 wMi the following operating condition*: wavelength 211 flW; Olit 4; lead hollow cathode tamp; air acetylene bun*r (O S k 110 mm Jf> wi#t supply of #ir *1 60 p*< (flow motor 9.0} ond acetylene or 10 pti (flow motor 9&} for on aspiretion roto of 0J ml/minute. M Stindird i>Um--Dissolve eny soluble lood salt In 4% ocotic odd lo o food concentration of 1 mg/ml. Dik/ts this tlondord stock solution with 4% ocotic odd to obtain working standards with final concentrations of 10, 30. 00 and 40 ug of load per ml. Pftptrttitu d Sample (leaching) Sofotloo (tnd>v*dweMy analyte 0 units of a#d umpkl Prior to analysis wash all vassals with household detergent. followed by a thor ough rn$ with d'ttillad water. Discard the water and dry tha unit; then fid each unit with 4% acetk acid so that the acid comes within %m of overflowing the con tainer. Measure the volume of odd. by difference, os the units ore being filled (use graduates or burets calibrated ">o deliver"). Cover each unit with a watch glass or other suitable cover, being sure not to allow the cover to coma in contact with the ecid. Lot stand at room tamparature for 24 hours. Drtanaimrits Stir sample (leaching) solution and determine absorbent* by atomic absorption spectrometry, diluting K required with 4% acetic acid. Determine the absorbent* of the sienderd solutions in s similar fashion. Prepare a standard curve of ab sorbance versus concentration. Determine the amount of lead from the ttenderd curve. Calculate results as ug of lead/ml of leaching solution. A sample is cswildsrsd yWiHn If fains TJ0 eg laad/ml ef leaching aetele* or - --v/- r. V :* : 11 iaoMrM.>..nLy?K3yi .r.-* 1 ""* REFERENCES 1. Anon., "trod Clitfi for Dtmtrrwrr. ILZJtO Mnwt Ceramic* #1," New York, toitnudonil Ud Zinc Research Organization, Ine,, 1970. L Ceramic Technical Commute*, Tud in the Ceramic Industrie*," New York, Lead Industrie* Association, Inc., 1996, Section 6. 1 C. F. Leiser. "Importance of Lead in Oats,* Cleat ladstry, 44 (9) 509-14i (10 ) 974-76, 594; (11) 630-33 (1963). 4. Orlowtid, H. and Marquia.). "Lead Replacement* in Dtnnenran flsm." JounuU of the America* Ceramic Society, M, (IS) 343-67 (1949). 9. Martjui*. J E., load in dares--Benefit* and Safety Precaution*." Procontingt. 1970 Fall Utrtimg. ifateriale aad Efaipmext o*d White Warn* DMikmi, America* Ceramic Society. Columbus. Ohio, American Ceramic Society (1971). 6. Koenig. ]. H, "Lead Frits and Flitted dare*," Ohio State Vntvmttg Saubet Emgtmerrtng Series. Vol VI, No. 1. Engineering Experiment Sudea Bulletin No. 99. July. 1937. 7. Martjui*. J. E. Op CM 6 VS. Bureau of Mine*. Information Circular 6436, fterpiratocy Tntecthe Oreicra Appmef By the Barra* of Mhsei at Of Decembtr 31. 1966: a revi sion of Information Circular 6291. Washington, D.C., by R. H Schotz and E J. IQooa, UA Bureau of Mines. DqX. of the Interior, (1969). . * LIA14559 ON-GLAZE DECORATIONS Tbc llj Food and Drug Administration baa recently reported that oo-giaae cala can be a tourer for teachable lead and cadmium If tbe decal la not prop erly formulated, applied and fired. Thia tame warning should apply to low tem perature decorations for glass (glass enamels) aa wsO. TESTING LABORATORIES Aa at July 10,1071, four laboratories in tbe U.S. were approved by tbe United States Potters Association for tbe performance of lead extraction testa on glarsd pottery. They were: Pittsburgh Testing Laboratory 130 Poplar Street Pittsburgh. Pennsylvania 15230 I Tbe Twining Laboratories. Inc. P.O. Box 1471 Fresno. California 0371* Bio-Technics Labs, lac. 1133 Crenshaw Bled. s Loe Angeles. California 00010 Coon Spectro-Cbendcal Laboratory PO Box 5865 Denver, Colorado 00117 i Hobby glare suppliers who were members I the U-S.P-A. "Ceramic 9Dtnnerwore Surveillance Program" os of July, 1971: 1. American Art Clay Co., Indianapolis, Indiana 2. American Beauty Ceramics. Willoughby, Ohio 3. Ceramichrome. Inc., Gardena, California 4. Ducan Ceramic Products, Inc.. Fresno. California 5. Care, Inc.. Haverhill. Massachusetts 6. Pctnbertoo-Nea] Ceramic Supplies, Bellflower, California 7. Reward Ceramic Color Mfrs.. Inc.. Glen Bunde, Maryland -',-4 S*' -4