ATLANTIC CITY -- Counterfeiters will bleach out $1 bills and try to print 20s on them. They glue party glitter on bills, which are run off on an inkjet printer, to give the numerals that new metallic look. They cut bills up and try to combine them into higher denominations, and hand the suckers 20s with George Washington's face on them.

They also like cities with big casinos, which means Atlantic City and Las Vegas, where they hope no one will notice that they bought a stack of chips with a few thousand in lunch paper, as the bogus bills are sometimes known, and then cashed the chips out for real currency.

And that is why the Treasury Department came to a big casino here on Tuesday to give its first public lesson about its new $50 bill, which is scheduled to be circulated in September.

"Casinos are big cash businesses, and they handle the larger denominations that counterfeiters work in," said Thomas A. Ferguson, director of the Bureau of Engraving and Printing.

So Ferguson and teams from the Secret Service and the Federal Reserve Bank of Philadelphia spent the morning at the Borgata casino, which alone handles $6 billion in cash in a year, telling chief cashiers and counters from the city's 12 casinos about the new bill. It still has Ulysses S. Grant gazing out with the poker face he might have shown Robert E. Lee at Appomattox, but the portrait is bigger than the one on the bill introduced in 1996. It has pinkish wavy stripes, color-shifting ink on the number "50" in the lower right-hand corner of the front side, a watermark duplicating Grant's face and "The United States of America" printed in scanner-defying letters along the edge of Grant's collar.

Purists who already miss the old one-color greenbacks -- the peach-colored $20 bill came out last fall -- the news is bad: The Treasury will try to stay ahead of counterfeiters and the digital technology they use by redesigning the currency every seven to 10 years from now on, said Melissa M. Tadeo, senior vice president of the Federal Reserve Bank of Philadelphia. Atlantic City takes in $3,000 to $7,000 a week in bad money -- a small but troublesome loss to the casinos, said Frank Benedetto, the Secret Service's special agent in charge in Atlantic City. Although dealers, change makers and cashiers are trained in spotting fakes, the casinos rely more than ever on "secure counters" -- scanning machines at cashiers' cages and in counting rooms, said Rosalie Lopez, head of cashier training at the Borgata.

In a demonstration, Lopez ran $10,000 in mostly genuine $20 and $50 bills through a scanner. It counted the cash and spat out the three fakes, planted by Benedetto, in a matter of seconds.

Slot machines are already equipped to detect fake money, and before long casinos will start installing the so-called secure counters at the last frontier for counterfeiters, the table games, where the gamblers' insistence on a fast pace leaves pit crews little time to check every bill.