Tea, Teapots, and Toxicity in the Seventeenth and Eighteenth Century

Abstract

Lead levels in the exterior and interior of seventeenth and eighteenth-century Chinese export ceramics were tested. A steeped water technique was used to examine the interior. XRF standard testing was used for the exterior. The results indicated that lead was present in some of the teapots. This suggests that some tea ingested during this early period was laced with lead, thereby countering the contemporary belief that drinking tea in that time period was preferable to other alternatives.

1. Introduction

Modern tea ingestion has been called ‘immune system boosting’ and ‘healthy,’ [1] among other positive attributes. Recently, however, attention has been drawn to the possible toxicity of modern tea consumption from exterior contamination. The kettle, heavy metals, and even the tea itself have been pointed to as culprits, among others.

In seventeenth- and eighteenth-century America, the attitude toward tea was quite similar to today’s in that tea supposedly promoted health and was even therapeutic. However, we know that at least some of the tea imported from China to Europe was packed in lead-lined containers during its ocean voyage, which took up to two or more years [2, 3]. (Figure 1) In addition, the tea caddies in which the tea was stored at its destination were often lead-lined [4, 5, 6, 7, 8, 9]. (Figure 2) While these were already dangerous, early pipes through which water flowed into household taps were lead-lined in some countries, such as England [10]. Lead contamination from these sources may have been minor, but there could be an accumulative impact.

Figure 1.

Gouache, one of twelve, illustrating tea production. Chinese laborers are packing tea with their feet, often in a lead lined container. Chinese export product, 1803. Private collection, H. 17.5 in.; W. 21.3 in. Thomas M. Mueller photography, Indianapolis, Indiana, USA.

Figure 2.

Pear shaped tea caddy similar to the lead lined caddies described in auction house records. England, eighteenth century. Private collection, H. 6.7 in.; W. 13.9 in. Thomas M. Mueller photography, Indianapolis, Indiana, USA.

2. Background for the study method

This study addresses this question using a unique analysis of lead within the pots by Dr. Shirley Maloney Mueller. This method will be referred to as the “steeped water method” for this discussion. The test reveals a way to look retrospectively for potential lead contamination within a teapot. While there are examinations in place to prove lead contaminates, such as X-ray fluorescence (XRF), these only show results of the exterior of objects. Dr. Mueller’s new approach to testing lead can give us information about inside teapots as well.

A series of Chinese export teapots dated 1690 to 1790 were examined (Chart). Teapots such as these were used in the colonies [11]. In the 1685 inventory, colonist Dr. Jacob De Lange wrote:

“The variety of form among this useful and decorative collection indicates that every sort of porcelain enjoyed in Holland would have been available to the rich in New Netherland…”

3. Methodology

Eight seventeenth and eighteenth-century Chinese export teapots (1690-1790) were tested for lead residual using the steeped water technique. This method is performed by boiling water in the pot, steeping it for 5 minutes, and then testing the water for lead contamination.

City tap water (Indianapolis, Indiana, USA) was boiled and then immediately poured into each pot. After 5 minutes, a water sample was transferred into special containers purchased from MACS Laboratory Inc. (Santa Clara, California). The samples were then sent back to this laboratory for analysis. This test center is a commercial analyzer for lead that uses Environmental Protection Agency (United States) approved methods. It is accredited by the State of California Department of Health.

4. Results

The chart below summarizes the results. Six of the eight vessels exhibited significant levels of lead (>1.5 micrograms/liter). Two of these six showed toxic lead levels (>15 micrograms/liter). Another two of the eight demonstrated acceptable levels (< 1.5 micrograms/Liter) as did the control, which was examined using a contemporary glass teapot. More about the dating and characteristics of early teapots, including the eight in this study, can be found in earlier articles by Dr. Mueller [12, 13, 14, 15].

The first steeped residual from the 1724 Davidson impaling Carr armorial porcelain teapot (Figure 3, left) tested at nearly twice the concentration of lead considered toxic (> 15 micrograms/liter), 26.9 micrograms/liter. Interestingly, the lead did wash out with a subsequent five-minute addition of boiling water. It was then reduced to today’s acceptable environmental level (1.5 to 15 micrograms/liter), 3.8 micrograms/liter.

Figure 3.

Chinese export porcelain dated 1724 on the left and a Yixing 1690 teapot on the right. Private collection. Left: H. 4.87 in; W. 7.0 in. Right: H. 4.2 in.; W. 5.0 in. Photos courtesy of the Indianapolis Museum of art, now Newfields, Indianapolis, Indiana USA.

The 1690 Yixing teapot (Figure 3, right) first steeped residual tested for a lead level of 20.4, well above the 15 micrograms/liter deemed toxic. The level dropped to 16.1 after a second addition of boiling water for 5 minutes, still above the poisonous level but lower than after the first steeping (Table 1). Yixing teapots were often left unwashed on the inside and the results of this “steeped water method” are in line with this concept.

Teapot	Date of teapot	Lead level 1st steeping micro grams/liter	Interpretation lead level
Davidson impaling Carr	1724	26.9	Toxic
Yixing Teapot	1690	20.4	Toxic
Blanc de Chine overdecorated in Holland	1690	2.8	High
Meissen inspired “Chinaman taking tea”	1740	5.2	High
Yixing, slip decorated	1740	7	High
Dated Anniversary for Norwegian market	1776	9.9	High
Double spouted vessel	1690	<1.5	Acceptable
American Flag	1790	<1.5	Acceptable
Contemporary Glass	2012	<1.5	Acceptable

Table 1.

Lead levels.

Four teapots dated 1690 to 1776 demonstrated lead levels (1.5 to 15 micrograms/liter) which were less than toxic. They averaged 6.2 micrograms/liter and are listed below from the lowest to the highest.

1. Blanc de Chine over-decorated in Holland, circa 1690, 2.8 micrograms/liter.

2. Meissen inspired “Chinaman taking tea,” circa 1740, 5.2 micrograms/liter.

3. Yixing, slip decorated, 1740, 7.0 micrograms/liter:

4. Dated Anniversary for the Norwegian market dated 1776, 9.9 micrograms/liter.

The final remaining two of the eight teapots measured below the environmental standard of lead, 1.5 micrograms/liter. They were the double-spouted vessel for tea or wine, 1690, and the American flag teapot, circa 1790.

To examine for lead on the exterior of the two pots that demonstrated toxic levels, Jennifer L. Mass, Ph.D., then Senior Conservation Scientist at Winterthur Museum in Delaware used X-ray fluorescence (XRF).

During XRF analysis, the surface of the object is bombarded with X-rays. The energy of these incoming X-rays is high enough to ionize atoms on the object’s surface, causing them to give off their fluorescent X-rays. The energies of the fluorescent X-rays emitted by the object are characteristic of the atoms it contains, and so this technique can be used to determine the elemental composition of a material, such as an overglaze enamel (or in the case of the Yixing pot, the outside of the body).

The 1724 Davidson impaling Carr armorial porcelain teapot did demonstrate lead in its outside glaze, though much less than the overglaze enamels. The exterior of the 1690 Yixing teapot did not test positive for lead.

5. Discussion

Higher than acceptable lead levels by today’s environmental standards were present in six of eight pots tested. Toxic levels of lead were present in two of these. The question is—what was the source of the lead?

Possibilities include residual tea contaminated with lead, evaporated water within the interior that was laced with lead, or, lastly, from the glaze within the porcelain teapots (the exterior of the Yixing teapot was lead-free). The latter possibility is unlikely for two reasons. One is that a high-fired glaze would not be expected to disperse into the solution at the relatively lower temperature of boiling water compared to the firing temperature used for the high-fired glaze. Secondly, the toxic level of lead in the 1724 Davidson impaling Carr teapot was lowered with a second steeping, indicating that the culprit responsible for the initial toxic level was washing out. This would not be expected if the lead level was due to the glaze within the teapot.

Further, in the 1724 armorial teapot, the base of the spout was strongly stained brown (Figure 4) and the glaze itself was eroded in this area. This wearing away could be because tea is acidic, and if left on a wet glaze repeatedly, it can be damaged. There was also dried brown matter initially in the bottom of the pot suggestive of remaining tea. Since the toxic lead level diminished with a second steeping, the residual tea was likely responsible for the initial excessive lead.

Figure 4.

Arms of Auchmuty teapot. Chinese export porcelain, 1750. The three tea stained straining holes represented here are like those in the 1724 arms of Davis impaling Carr (the arms of Davis impaling Carr is unavailable for photography). Private collection, H. 5.12 in; W. 7.5 in. Thomas M. Mueller photography, Indianapolis, Indiana, USA.

The Yixing teapot, on the other hand, is a different specimen altogether than the glazed porcelain pots. Though its exterior body did not contain lead, it is porous, unlike porcelain teapots which are impermeable when intact [15]. This porosity is consistent with the novelty that the Chinese ascribed to Yixing teapots. After a time, tea did not need to be added to the vessel to make tea because it permeates into the interior of the pot in earlier brews. This means that boiled water alone added to a Yixing pot (without tea) would result in tea released from the vessel’s interior. The same could be true for any residual lead that was remaining from making lead-laced tea.

On the other end of the spectrum from toxic, two pots demonstrated lead levels within the acceptable environmental standard. They were the 1690 double-spouted pot and the 1790 American flag teapot. One explanation for the 1690 pot is that it was never used for tea, but instead for wine or condiments or not at all. There was no tea stain at the base of either of the two spouts.

The 1790 teapot, on the other hand, was used for tea. There were dark stains around and about the straining holes at the base of the spout that confirm this. Likely, this took place in the 1800s in America since the flag on the pot indicates it was destined for this country. Lead pipes were not installed in United States municipalities until the late nineteenth and early twentieth century. Thus, the water poured into the teapot may not have been lead-ridden unless it was used after the late 1800s. Also, the tea carried to America may not always have been stored in lead-lined chests or tea caddies this late.

6. Limitation of this study

There is a limitation of this study that could not be avoided. The teapots examined were executed in China 200 years or more ago. We do not know when they were used for tea during their timespan, if at all. What we can say is that pots that showed toxic lead levels did have lead contamination. Any adulteration likely would have been earlier in the teapot’s history rather than later because as the vessels aged, they were perceived to be valuable and, therefore, likely not used.

7. Conclusion

Sources for lead poisoning in early America have been reported in multiple studies. They included pewter, pottery, crystal, paint, and solder [16]. The discovery of lead in exhumed bones from this period provides further documentation [17]. Now, tea itself, at least in some cases, can be added to the list, almost certainly due to contamination with lead from extraneous sources.

In summary, the results of this study suggest that early tea drinking did not necessarily counter the negative effects of drinking unboiled germ-laden fluids or alcohol. Instead, sometimes, it simply substituted one poison for another. How this made people ill during this period and how ill it made them can only be conjectured. However, Dr. Mueller’s tests reveal that lead contamination was spread through drinking tea using a new methodology. Hopefully, these results will make way for more scientists and art historians to study the effects of lead in ceramics in the seventeenth and eighteenth centuries.