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Uranium and Ceramics

Translated by Edouard Bastarache
Here is through some excerpts of articles by authors having published works on ceramics (of which some became very rare) during the 19th. and 20th. century, an outline of what was the primarily use of uranium and compounds in ceramic products, essentially devoted to the manufacture of vitrifiable colors, colouring materials for enamels, lustres and glazes.
Nowadays, these products are part of the history of ceramics and are not used anymore in the current manufacture of ceramic wares in the Western world. The toxicity of uranium and compounds and their radioactivity have placed these materials under close scrutiny with a formal ban on their trade and use.
Excerpts on the use of uranium and compounds in ceramics :
1) In the book "Traité des Arts Céramiques ou des poteries", Alex. Brongniart, January 1854 :
Uranium oxide, suitably prepared, can give a yellow-orange color of a great vividness which one obtains only with difficulty using potash antimoniate.
One obtains yellows by means of potash antimoniate and lead oxide. It is close to the " Yellow of Naples ", more or less darkened by the addition of varying amounts of zinc oxide, iron oxide and sometimes tin oxide. One can still add uranium oxide in order to obtain a darker yellow.
Vitrifiable color for porcelain :
(Uranium oxide yellow-orange which is used for backgrounds)


Yellow-Orange n° 45

" Rocaille " flux (75% minium, 25% silica)


Pure uranium oxide


The preparation of the oxide is carried out by treating pitchblende with acidic solutions.
2) In the book "Leçons de Céramique", volume 1, Alphonse Salvétat - 1857 :
Uranium oxide (U3O8 or saline oxide) is used in glassmaking to produce varied tones of yellow with green glints named " dichroic ". Their use in arts to decorate porcelain is rather important.
Vitrifiable uranium oxide yellow for decorating on hard porcelain at 950°C :


Vitrifiable uranium yellow

Flux n°6


Uranium oxide yellow (Sodium Uranate)


Composition of the flux :


Flux n°6

Minium Pb3O4


Crystallized Boric Oxide


Crushed Quartz


3) In the book " Fabrication industrielle des Porcelaines " volume II by Marc Larchevêque - 1929 :
Uranium oxide and various compounds make up part of the artificial colouring materials that can be used at 1400°C (cone 14) just as metals, oxides and compounds of the following elements: chromium, cobalt, iron, manganese, nickel, vanadium, tungsten, titanium, gold, platinium, iridium.
The main uranium ore is pitchblende which contains between 40 and 90% of the uranium oxide U3O8, the remainder being made up of sulphur, arsenic, iron, lead and a negligible quantity of radium and other radioactive elements.
Sodium uranate (Na2O (UO3)2.6H2O) is designated by the unsuitable name "Yellow uranium oxide ".
Uranyl nitrate (a salt with light yellow-green crystals), is used in the preparation of various liquid colours (lustres).
Other compounds used : ammonium uranate, potassium uranate, uranium oxides, calcium uranate, magnesium uranate, iron uranate, manganese uranate, lead uranate, etc...
Recipe for the uranium oxide yellow-orange for vitrifiable color (between 900°C and 950°C) :


Vitrifiable uranium yellow-orange

Flux n°1 (also named "rocaille" flux)


Ammonium uranate


To mix, melt, crush and dry.
Flux n°1 :


Flux n°1

Litharge (PbO)

75 (or minium Pb3O4, 76.8)

Crushed quartz


4) In the book "La Bible du Céramiste" Anonymous - about 1965 :
There are three significant uranium oxides :
a) Uranium dioxide or uranous oxide UO2, black, molecular weight 270.14.
b) Uranium uranate U3O8, green olive, molecular weight 842.42.
c) Uranium trioxide or uranyl oxide UO3, red, molecular weight 238.14.
All of these oxides are insoluble in water, soluble in hydrochloric and sulphuric acids and are toxic.
At high temperature, the uranium dioxide changes into uranium uranate.
Uranium oxides are used mainly as colouring materials for enamels, glass and porcelain, though the relative instability of the colours restricts their use.
a) Uranium dioxide colours glazes in black, jet black or gray in reducing atmosphere and yellow in oxidizing atmosphere. It is also used to prepare black and brown colouring materials for porcelain.
b) Uranium uranate behaves in a similar way, by giving blacks, browns and grays in reducing atmosphere and yellows or reds according to circumstances, in oxidizing atmosphere.
c) Uranium trioxide gives greens or blacks in reducing atmosphere and yellows in oxidation.
This oxide is used to colour under-glazes and porcelains, but its used is limited, because of its high price, to lead glass to which it gives a vivid orange yellow colour.
Uranium trioxide is sometimes used as an agent of crystallization in crystalline coloured glazes.
One uses it in glassmaking, only or with cadmium sulphide, for the production of glass intensely coloured in yellow and orange.
Exemples of recipes for red orange glazes, to be fired at low temperature between cone 08 and cone 06 :


Possible amounts

Lead carbonate

64 à 66 %

Crushed silex

18 à 13 %

Zinc oxide

4 à 3 %

Black uranium oxide (dioxide)

14 à 15 %


0 à 3 %

Another uranium compound : Uranium nitrate
This lemon-yellow salt is used in the composition of lustres, of which one of these is prepared with 2 parts of resin soap, 4 parts of hot water, and 1 part of an uranium nitrate solution. The uranium soap obtained is mixed with an essential oil.
5) In the book "La céramique de A à Z" par J. Rigaud - vers 1975 :
There are three current forms of uranium oxides :
1)Uranous oxide or uranium dioxide (" reducing " UO2) :
Uranous oxide is extracted from pitchblende or carnotite by a process based on nitric acid.
2) Uranic oxide or uranium trioxide ("oxidizing" UO3) :
Uranium trioxide UO3, or uranic oxide, is obtained by oxidation at high temperature of "saline" oxide U3O8. It takes up a yellow color and can take up the hydrated form UO3.H2O or UO2 (OH)2, uranyl hydroxide.
It can form uranates and diuranates with bases. These products intervene in glassmaking and ceramics in the colouring of the vitreous phases and the preparation of pigments for high temperature firing.
Thus the introduction of alkaline diuranates into glasses leads to yellow by transmission, green by reflection; moreover these glasses become dichroic and fluorescent under ultraviolet rays.
In ceramics, the uranates of heavy metals (Mn, Fe, Pb...) are at the base of colors used under glazes, called yellows of uranium oxide, obtained in oxidation firing.
3) "Saline" uranium oxide U3O8, the most stable :
Saline oxide U3O8 or uranium oxide is found naturally in pitchblende, which can contain some up to 80%. U3O8 is used in ceramics and glassmaking to make uranates.
6) In the book "Keramic-Glasuren" by Stefanov et Batschwarov - 1988 :
Yellow coloring materials :
The oxide of uramium in the presence of silica or alumina makes it possible to obtain yellow hues, but it is not used any more taking radioactivity into account.
Yellow glazes :
Lead/calcium or lead/zinc glazes develop a yellow hue by the addition of uranium oxide. Just as not very alkaline lead/boron glazes become yellow by the addition of 5% of sodium uranate.
Red glazes :
Lead/zinc glazes containung calcium or boron produce an intensive red hue by addition of 10% of uranium oxide.

Components :

Red Glaze

Red Orange Glaze

Minium (Pb3O4)



Potassium feldspar



Crushed silica



Sodium uranate



Uranium oxide



Zinc oxide






Uranium lustre:

Uranium lustre is obtained by the fusion of rosin (colophony), on a sand bed, added with 30g. of uranyl acetate, then dissolved in 300 ml of hot spirit of turpentine. After cooling the mixture is allowed to settle (and decant) and preserved two to three days before the first use.

Smart.Conseil / April 2002


References :
"Traité des Arts Céramiques ou des poteries", Alex. Brongniart, Janvier 1854
"Leçons de Céramique", tome 1, Alphonse Salvétat - 1857
"Fabrication industrielle des Porcelaines" tome II par Marc Larchevêque - 1929
"La Bible du Céramiste" Anonyme - Origines de publication inconnues - vers 1965
"La céramique de A à Z" par J. Rigaud - vers 1975
"Keramic-Glasuren" de Stefanov et Batschwarov - 1988
On this page : Uranimum and ceramics, Toxicology : Depleted uranium, Articles : Contamination by uranium-containing ceramic wares

 Since uranium acts on body organs and tissues in the same way as Depleted Uranium (DU) the results and conclusions from uranium studies are considered to be broadly applicable to DU.
However, in the case of effects due to ionizing radiation DU is less radioactive than uranium.
Uranium :
1-Uranium is a silver-white, lustrous, dense, natural, weakly radioactive element. It is ubiquitous throughout the natural environment, and is found in varying but small amounts in rocks, soils, water, air, plants, animals and in all human beings.
2-On average, approximately 90 µg (micrograms) of uranium exist in the human body from normal intakes of water, food and air. About 66% is found in the skeleton, 16% in the liver, 8% in the kidneys and 10% in other tissues.
3-Natural uranium consists of a mixture of three radioactive isotopes which are identified by the mass numbers 238U(99.27% by mass), 235U(0.72%) and 234U(0.0054%).
4-Uranium is used primarily in nuclear power plants. However, most reactors require uranium in which the 235U content is enriched from 0.72% to about 3%.
Depleted uranium :
1-The uranium remaining after removal of the enriched fraction contains about 99.8% 238U, 0.25% of 235U and 0.001% 234U by mass; this is referred to as depleted uranium or DU.
2-DU is weakly radioactive and a radiation dose from it would be about 60% of that from purified natural uranium with the same mass.
3-The behaviour of uranium and DU in the body is identical radiologically and chemically.
4-Spent uranium fuel from nuclear reactors is sometimes reprocessed in plants used for natural uranium enrichment. Some reactor-created radio-isotopes can consequently contaminate the reprocessing equipment and the DU. Under these conditions another uranium isotope, 236U, may be present in the DU together with very small amounts of the transuranic elements plutonium, americium and neptunium and the fission product technetium-99. However, on the basis of the concentrations of these radio-isotopes found in DU, the increase in radiation dose from uptake by the human body would be less than 1%.
Applications of depleted uranium :
1-The main civilian uses of DU include counterweights in aircraft, radiation shields in medical radiation therapy machines and containers for the transport of radioactive materials.
2-Due to its high density, about twice that of lead, and other properties, DU is used in munitions designed to penetrate armour plate and for protection of military vehicles such as tanks.
Exposure to uranium and depleted uranium :
1-The average annual intakes of uranium by adults are estimated to be 460 µg from ingestion and 0.59 µg from inhalation.
2-Under most circumstances, use of DU will make a negligible contribution to the overall natural background levels of uranium in the environment. The greatest potential for DU exposure will follow a conflict where DU munitions are used.
3-A recent United Nations Environment Programme (UNEP) report giving field measurements taken around selected impact sites in Kosovo (Federal Republic of Yugoslavia) indicates that contamination by DU in the environment was localized to a few tens of metres around impact sites. Contamination by DU dusts to local vegetation and water supplies was found to be extremely low. Thus, the possibility of significant exposure to the local populations was found to be very low.
4-However, levels of DU may be significantly raised over background levels in close proximity to DU contaminating events. Over the days and years following such an event, the contamination will become dispersed into the wider natural environment. People living or working in affected areas can inhale dusts and can consume contaminated food and drinking water.
5-There is a possibility that people near an aircraft crash may be exposed to DU dusts if counterweights were to combust on impact. Significant exposure to people from this situation would be rare. Exposures to clean-up and emergency workers following aircraft accidents are possible, but normal occupational protection measures would prevent any significant exposure occurring.
DU exposure pathways :
1-Individuals can be exposed to DU in the same way they are routinely exposed to natural uranium, i.e. through inhalation, ingestion, dermal contact or injury (e.g. embedded fragments).
2-Each of these exposure situations needs to be assessed to determine any potential health consequence.
3-The relative contribution from each of these pathways to the total DU uptake into the body depends on the physical and chemical nature of the DU, as well as the level and duration of exposure.
Intake of depleted uranium :
1-Intake by ingestion can occur if drinking water or food is contaminated by DU. In addition, the ingestion of soil by children via geophagia (the practice of eating earth, clay, chalk, etc.) or hand-to-mouth activities is also an important pathway.
2-Intake by inhalation can occur following the use of DU munitions during or when DU deposits in the environment are re-suspended in the atmosphere by wind or other forms of disturbance. Accidental inhalation may also occur as a consequence of a fire in a DU storage facility, an aircraft crash, or the decontamination of vehicles from within or close to conflict areas.
3-Intake by contact exposure of DU through the skin is very low and relatively unimportant.
4-Intake from wound contamination or embedded fragments in skin tissues allows DU to enter the systemic circulation.
Absorption of depleted uranium :
1-Most (>95%) uranium entering the body via inhalation or ingestion is not absorbed, but is eliminated via the faeces.
2-Of the uranium that is absorbed into the blood, approximately 67% will be filtered by the kidney and excreted in the urine within 24 hours; this amount increases to 90% within a few days.
3-Typical gut absorption rates for uranium in food and water are about 2% for soluble uranium compounds and down to 0.2% for insoluble uranium compounds.
Health effects of exposure to depleted uranium :
DU has both chemical and radiological toxicity with the two important target organs being the kidneys and the lungs.
1-In the kidneys, the proximal tubules are considered to be the main site of potential damage. Long-term studies of workers chronically exposed to uranium have reported impairment of the kidneys that depended on the level of exposure. There is also some evidence that this impairment may return to normal once the source of excessive uranium exposure has been removed.
2-In a number of studies on uranium miners, an increased risk of lung cancer has been demonstrated, but this has been attributed to exposure from radon decay products. There is a possibility of lung tissue damage leading to a risk of lung cancer if a high enough radiation dose results from insoluble DU compounds remaining in the lungs over a prolonged period (many years).
3-Erythema (superficial inflammation of the skin) or other effects on the skin should not occur even if DU is held against the skin for prolonged periods (weeks). There is no established data to suggest that skin cancer results from skin contact with uranium dusts.
4-No consistent or confirmed adverse effects have been reported for the skeleton or liver. However, few studies have been conducted.
5-No reproductive or developmental effects have been reported in humans, but studies are limited.
6-Although uranium released from embedded fragments may accumulate in the central nervous system (CNS) tissue and some animal and human studies are suggestive of effects on CNS function, it is difficult to draw firm conclusions from the studies.
Maximum radiation exposure limits :
The following doses, from the International Basic Safety Standards agreed by WHO in 1996, are in addition to those from normal background exposures.
1-The general public should not receive a dose of more than 1 millisievert (mSv) in a year. In special circumstances, an effective dose of up to 5 mSv in a single year is permitted provided that the average dose over five consecutive years does not exceed 1 mSv per year. An equivalent dose to the skin should not exceed 50 mSv in a year.
2-Occupational exposure should not exceed an effective dose of 20 mSv per year averaged over five consecutive years or an effective dose of 50 mSv in any single year. An equivalent dose to the extremities (hands and feet) or the skin should not surpass 500 mSv in a year.
Guidance on exposure based on chemical and radiological toxicity :
The World Health Organization (WHO) has guidelines for determining the values of health-based exposure limits or tolerable intakes (TIs) for chemical substances. The TIs given below are applicable to long-term exposure in the general public (as opposed to workers). In single and short-term exposures, higher exposure levels may be tolerated without adverse effects.
1-The general public's intake via inhalation or ingestion of soluble DU compounds should be based on a tolerable intake value of 0.5 µg per kg of body weight per day. This leads to an air concentration of 1 µg/m3. For ingestion, this would be about 11 mg/y for an average adult.
2-It would be appropriate to reduce the TI for intake of insoluble DU compounds to 0.5 µg per kg of body weight per day so that compatibility is achieved with the public radiation dose limit. When the solubility characteristics of the uranium species are not known, which is often the case in exposure to depleted uranium, it would be prudent to apply the more stringent tolerable intakes, i.e., 0.5 µg per kg of body weight per day for oral exposure.
Uranium compounds with low absorption are markedly less nephrotoxic, and a tolerable intake via ingestion of 5 µg per kg of body weight per day is applicable.
Monitoring and treatment of exposed individuals :
1-For the general population, neither civilian nor military use of DU is likely to produce exposures to DU much above normal background levels produced by uranium. Therefore, an exposure assessment for DU will normally not be required.
2-When an individual is suspected of being exposed to DU at a level significantly above the normal background level, an assessment of DU exposure may be required. This is best achieved by analysis of daily urine excretion. The amount of DU in the urine is determined from the 235U:238U ratio, obtained using sensitive mass spectrometric techniques. Faecal measurement can give useful information on intake if samples are collected soon after exposure (a few days).
3-External radiation measurements over the chest, using a whole-body radiation monitor for determining the amount of DU in the lungs, have limited application since they require specialist facilities and can only assess relatively large amounts of DU in the lungs.
4-There are no specific means to decrease the absorption of uranium from the gastrointestinal tract or lungs, or increase its excretion. Thus, general methods appropriate to heavy metal poisoning could be applied. Similarly, there is no specific treatment for uranium poisoning and the patient should be treated based on the symptoms observed. Dialysis may be helpful in extreme cases of kidney damage.
Recommendations :
1-Levels of contamination in food and drinking water could rise in affected areas after some years and should be monitored where it is considered that there is a reasonable possibility of significant quantities of DU entering the ground water or food chain.
2-Where possible, clean-up operations in impact zones should be undertaken where there are substantial numbers of radioactive projectiles remaining and where qualified experts deem contamination levels to be unacceptable. If very high concentrations of DU dust or metal fragments are present, then areas may need to be cordoned off until removal can be accomplished. Disposal of DU should come under appropriate national or international
recommendations for use of radioactive materials.
3-Young children could receive greater exposure to DU when playing in or near DU impact sites. Typical hand-to-mouth activity could lead to high DU ingestion from contaminated soil. Necessary preventative measures should be taken.
4-Individuals who believe they have had excessive intakes of DU should consult their medical practitioner for an examination and treatment of any symptoms. General screening or monitoring for possible DU related health effects in populations living in conflict areas where DU was used is not called for.
Reference :
The WHO, Depleted Uranium, Fact Sheet N° 257, Revised April 2001
On this page : Uranimum and ceramics, Toxicology : Depleted uranium, Articles : Contamination by uranium-containing ceramic wares

1) Accidental contamination from uranium compounds through contact with ceramic dinnerware, by Ralph W. Sheets, Clifton C. Thompson
ABSTRACT: Examination of orange-colored dinnerware samples purchased in antique stores and flea markets has revealed the occasional presence of surface uranium compounds that are readily transferred to the hands and
clothing. We have further been able to produce soluble uranium compounds on the surfaces of clean dishes by exposing them to household vinegar or bleach. We estimate that handling of a contaminated dish can transfer up to
1-2 becquerels or more or uranium compounds to the hands. Uranium contamination is of concern because the element is not only an alpha emitter but also a chemical nephrotoxin. Although the amount of uranium likely to
be ingested as a result of casual handling may be small, it could still exceed by several times the amount occurring in the average diet (about 40 mBq/day). Furthermore, since fresh surface compounds are readily formed, it is possible that a person who regularly handles or eats from uranium-glazed dinnerware can accidently ingest significant amounts of uranium.
2) Release of uranium and emission of radiation from uranium-glazed dinnerware, by Ralph W. Sheets, Sandra L. Turpen
ABSTRACT: Samples of orange, yellow, beige, ivory and blue-green ceramic dinnerware glazed with uranium compounds have been examined. Measurements at glaze surfaces yielded exposure rates of 3.8-16 mR/h (1-4 uC/kgh) for orange glazes and rates of 0.04-1.3 mR/h (0.01-0.3 uC/kgh) for ivory, beige, and yellow glazes. Whole body exposure from a shelf display of 40 orange dishes was estimated to be 0.1-0.5 mR/h(0.03-0.13 uC/kgh), or up to 50 times the room background radiation level, at a distance of 1 meter. Twenty-four hour leaching tests of orange, yellow, and ivory dishes were carried out with various concentrations of acetic and citric acids. Uranium concentration in leachates of some orange dishes exceeded 450 mg/L. Uranium is a chemical
nephrotoxin and the United States Environmental Protection Agency has proposed a maximum contaminant level for drinking water of 0.020 mg/L. Based on this value a person consuming 2.2 L of drinking water per day would ingest 0.31 mg of uranium per week. A person eating once a week from an orange glazed dish could easily ingest 10 or more times this amount.

By Edouard Bastarache

Related Information


Typecodes Article by Edouard Bastarache
Edouard Bastarache is a well known doctor that has written many articles on the subject of toxicity of ceramic materials and books on technical aspects of ceramics. He writes in both English and French.
Materials Uranium Oxide
Materials Uranyl Nitrate
Hazards Uranium in Ceramic Glazes
Extracts from a discussion (between technicians knowledgeable on the subject) about the safety of using uranium in ceramic glazes.

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