They also found that the Governor held a 49 to 37 percent overall lead in the gubernatorial contest.
It cannot be used to clean highly contaminated sites, however, like those with more than 1 percent lead in their soil.
This compares with an 82 to 3 percent lead in February.
In one sample, the product contained 80 percent lead.
Despite a record 10.7 million unique users in January, it managed only a 13 percent lead over the next competitor.
The incumbent holds a commanding 40 percent lead, according to the survey.
Brass is an alloy that can be up to 8 percent lead.
Samples of it contained up to 80 percent lead.
Also, when compared to other polls, the six percent lead was an outlier.
Crystal is at least 24 percent lead, and therefore reflects more light than does glass.