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VOSI - Public Health Standard V50.1
Research Report 7

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Public Health - VOSI Research Report RR7-V50.1
Updated: 12-08-2000

"UNIVERSAL SPECIFICATION/TEST METHOD FOR CLASSIFYING AND MINIMIZING THE LEAD CONTENT OF METAL CORE CANDLE WICKS & TO BAN METAL CORE IMPORTED CANDLES"

REFERENCES

  1. Model 90 Candle Wick Core Classification Test Kit; Technical Products Co., N. Caldwell, NJ 07006

  2. Material Safety Data Sheet (MSDS) for (Wire) Zinc Base Alloys; Wire Industries, Inc., Dumar, AR

  3. MSDS for Tin/Copper, Antimony/Silver Alloy; Federated-Fry Metals, Altoona, Pa

  4. Technical Report 17700, 8/2/2000; Intertek Testing Services, Totowa, NJ

  5. Technical Report 17810, 9/12/2000; Intertek Testing Services, Totowa, NJ

  6. ASTM E1613-99 "Standard Test Method for Determination of Lead by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES), Flame Atomic Absorption Spectrometry (FAAS), or Graphite Furnace Atomic Absorption Spectrometry (GFAAS) Techniques

  7. ASTM Proposed 9/00 "Standard for Lead (Pb) Content in Wicks Used in the Production of Candles"

  8. Adams & Pearce 11/99 Pricelist for cotton, paper & zinc core wicks

SCOPE

To classify the metal core of candlewicks based on the tensile strength of zinc, tin and lead cores and to measure the lead content of it.

To determine if the tensile strength of zinc alloys correlates with the lead content when tested per ref. 6.

To determining the burning rate of tealight candles with zinc, tin, lead, paper and cotton core wicks.

CLASSIFICATION & % LEAD

The following tin and zinc core candlewicks were received from Jeb Head, chairman of the ASTM Candlewick Task Group, of Atkins & Pearce, Inc., Covington, KY:

tin core wicks

zinc core wicks

(1T) 51-31=18T

(1Z)51=36=18Z

(2T).36-24-24T

(2Z) 36-24=24Z

(3T)10-38T

(3Z) 32-10=38Z

Using the Technical Products Model 90 Wick Classification Test Kit (ref. 1), tensile tests were performed on the aforementioned six tin and zinc core wicks. In addition the writer had a box of lead core candles with no identification except the word "citronella"; one of the lead core candles was tested.

The ref. 4 test report for % lead is summarized in Table 1 for the tin, zinc and lead core wicks. An unwaxed cotton wick contained 0.003% Pb. A waxed cotton wick contained 0.006% Pb. A red imported candle was supplied by Jim Becker (American Greetings, Inc.) chairman of ASTM F 15 "Consumer Products" subcommittee F15.45 on "Candle Products" and ASTM Task Group on Candle Wicks member, supplied both the red imported candle and tealights for VOSI testing. The red imported candle, without a metal core, contained 0.008% Pb and the imported tealight candle wick, without metal core, contained 0.003% Pb. These values prove that the maximum % lead should be set at 0.010% (100 ppm)

Table 1 summarizes the tensile tests and lead content of the tin, zinc and lead wicks.
F1 is the uncorrected breaking force, and
F2 is the corrected force after calibrating the force gage.
D is the core wire diameter, inches, before testing and is the diameter used for calculating S, the tensile stress, in psi.

The % lead was measured in accordance with ref. 6 by Intertek (ref. 4) using the Inductively Coupled Argon Plasma test method which is accurate to 10 ppm (.001%).

Table 1.

Tensile Strength & Lead Content of Metal Cores

 

Tin

Zinc

Lead

1T

2T

3T

1Z

2Z

3Z

1L

Dia.

0.0185

0.0187

0.0117

0.0139

0.0143

0.0143

0.0183

F1-lb

1.78

1.75

0.51

3.78

3.95

4.07

0.52

F2-lb.

1.50

1.45

0.35

3.60

3.72

3.80

0.32

S psi

5566

5283

3247

23663

23176

23675

1106

S- Average

 

4700

   

23505

 

1106

Lead - %

0.04

0.04

0.026

0.006

0.006

0.01

18.3

Lead Average

 

0.023

   

0.007

 

18.3

A metal core candle wick, Walnut Hill Co., Bristol, Pa, 10 ft. long and designated W-1 wire, B-1 braid for candles less than 2" diameter, was purchased by the writer at a craft shop. The tensile strength of this material at 0, 5 and 10 ft. were 15,312, 18,119 and 18, 178 respectively.

The lead content, tested per ref. 5 at 0, 5 and 10 ft, was 0.016, 0.014 and 0.015 respectively. Since the Table 1 minimum tensile strength was 23,176 for this "special high grade zinc alloy" and the maximum % lead was 0.010% the % lead appears to vary inversely with the strength, and quality of the zinc alloy. The 0.01 % lead is greater than the 0.006% maximum lead specified on the MSDS (Ref 2.).Further testing is required to determine whether tensile testing can be used to classify the % lead of zinc alloy metal cores in addition to determining whether the core is tin or lead. This could eliminate the need to use the ref. 6 sophisticated test method for insuring that zinc alloys contain less than 0.010% lead.

Based on the above, the breaking force (F2), based on a minimum 20,000 psi tensile strength for a high grade zinc alloy with .01% maximum lead content is listed in Table 2. and ref. L, based on wire diameters from 0.010 to 0.020 inches.

Table 2.

Breaking Force (F2) vs. Zinc Core Diameter

 

0.010

0.011

0.012

0.013

0.014

0.015

0.016

0.017

0.018

0.019

0.020

F2-lbs

1.6

1.9

2.3

2.7

3.1

3.5

4.0

4.5

5.1

5.7

6.3

BURNING RATE

Tealight candles, from American Greetings (black cherry), having a l 7/16" diameter and 5/8" height and .090 center hole diameter, were used for evaluating the burning rate of the candles using tin and zinc metal core wicks and paper and cotton core wicks supplied by Atkins & Pearce, Inc. The wicks were wax coated by dipping in the same melted wax as the tealight candles used. In addition the previously mentioned lead core citronella votive candle was tested.

Table 3. lists the wick diameter (D), weight of the candle wax both before and after testing in a ventilated hood, and the burning rate in minutes/gm of candle wax.

Table 3.

Burning Rate

 

Tin

Zinc

Paper

Cotton

Lead

Wick Dia. in.

0.065

0.057

0.078

0.065

0.070

Initial Wgt. - gm

15.2

15.2

15.2

15.4

52

Final Wgt. - gm

0.7

0.7

0.4

14.5

10

Burn Time min.

178

215

158

----

542

Minutes/gm

12.3

14.8

10.7

----

12.9

Ranking (slow)

3

1

4

 

2

Table 3. indicates that zinc core candles have the slowest burning rate and paper the fastest. Lead was supposedly used because of its slow burning rate however zinc is superior to lead. The cotton core candlewick quickly extinguished itself. Based on the highest burning rate, the paper core wick would be the most profitable to use and would eliminate the need to use any metal core wick.

CONCLUSIONS

  1. The .01% maximum lead content can be met in high-grade (high tensile strength) zinc alloy cores.

  2. Paper core wicks can be used to replace all metal cores by sacrificing long burn time.

  3. Tensile strength can be used to classify metal core wicks in order to ban the use of tin and lead cores.

  4. Tensile testing is the only practical way for custom inspectors to test imports for lead or zinc content. A visual inspection can be used to ban imported metal core wicks and candles.

  5. Further testing is required to verify that tensile testing of zinc alloys can be used to measure the .01% maximum lead content and eliminate the use of a sophisticated laboratory test method (ref. 6).

  6. Western Europe has banned metal core candle wicks. The United States, as a World Health Organization (WHO) member, should use public health standards which are equal to or better than those of any WHO member nation.

 

 ADDENDUM : 12-08-2000

TENSILE STRENGTH & % LEAD IN WIRE INDUSTRY'S 308 ZINC ALLOY WIRE

A 10 foot long sample of 0.014" diameter was cut in half. Six wires, 2" long were cut from one end and three pieces were cut from the other end of each 5' length. Each piece was identified as 1, 1A, 1B, ....6, 6A, 6B and placed in separate envelopes before testing.

TENSILE STRENGTH

Test By Don Meserlian,P.E. 
Date Tested: 11/17/00
Test Method: VOSI V50.1 "Universal Specification/Test Method for Classifying and Minimizing the Lead Content of Metal Core Candle Wicks"
Test Instrument: Micrometer, Technical Products Model 90 Candle Wick Core Classification Test Kit

Table 4.

1

2

3

4

5

6

Avg. Std. Dev.

Diameter-in

.0150

.0151

.0152

.0151

.0149

.0150

~ ~

Force - lbs.

3.8

4.0

4.1

4.1

3.7

3.8

~ ~

Tensile str.-psi
x 1000

21.5

22.4

22.6

22.9

21.2

21.5

22.0

0.67

% LEAD - TEST LAB A

Test Lab: Intertek Testing Lab, Springfield, N.J.
Date Tested: 11/30/00
Test Method: Inductively Coupled Argon Plasma (ICP)
Test Instrument: Atomscan "Advantage" ICP

Table 5.

1A

2A

3A

4A

5A

6A

Avg. Std. Dev.

PPM

61.0

81.0

54.2

101.4

91.7

104.9

82.4 20.0

0.006

0.008

0.005

0.010

0.009

0.011

0.008

~

% LEAD - TEST LAB B

Test Lab: SGS/U.S. Testing, Fairfield, N.J.
Date Tested: 11/30/00
Test Method: Atomic Absorption Spectroscopy (AAS) (nitric acid digestion)
Test Instrument: Varian Flame AAS, Model AA-20

Table 6.

1B

2B

3B

4B

5B

6B

Avg. Std. Dev.

PPM

24.9 

25.5  

14.3 

*15.2

17.8 

20.8

20.7 4.8

0.003 

0.003 

0.001 

*0.015  0.002

 0.002 

0.002 ~

* Discount reading.

Note: Maximum permissible lead 0.01% per VOSI V50.1

RR7-50.1, ref. 2, Material Safety Data Sheet (MSDS) specifies: "Lead Range 0 - .006%"

The average % of Lab B, using AAS, is 0.002% whereas the Lab B ICP method was 0.008%.

CONCLUSIONS

  1. Use only AAS for measuring the % lead in metal core candle wicks. The 308 zinc alloy manufacturer uses AAS. This further confirms the validity of VOSI V50.1. 

  2. Lab B tested a 32" (0.51 gm) sample of the same wire 12/6/00 and measured 20.4 PPM of lead. 
    This agrees closely with the 20.7 above average; both are 0.002% lead.

  3. Manufacturers of zinc core wicks should provide certification that the lead content is less than 0.01%. This certification may be used in lieu of AAS testing.

Donald C. Meserlian, P.E.
VOSI Chairman

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Created: 2000-10-27 Last Updated: 2002-04-16