Markes International, a leading manufacturer of sorbent sample tubes, has adopted a new glass tube marking system. Developed by specialist ceramic decal 

company Xerital, the system uses serialized barcodes that can be applied to glass substrates.

Xerital’s high-temperature decals incorporate the barcode and are actually fired onto the glass tubes, resulting in a permanent marking that is strongly resistant to scratching, chemical attack, and thermal processes. The final, fired product is not only extremely durable but provides for the high-resolution output that is vital for accurate code scanning and reading. Already successfully applied in sanitaryware production, where the firing temperature is more than 1200°C, the barcodes yield valuable information regarding product tracking, operative performance, warehousing and stock control.

Improving Efficiencies

For over a decade, Markes International, which is based in the South Wales town of Llantrisant, has pioneered analytical thermal desorption (TD) instrumentation and associated sampling equipment. Markes also reportedly offers the widest range of TD consumable products on the market. As a world leader in TD technology, Markes International’s ethos is firmly focused on innovation and designing products that help make its customers’ lives easier.

This commitment led to the company’s decision to enhance its sorbent tube labeling. The tubes are used for capturing volatile organic compounds (VOCs) from the air, with subsequent laboratory analysis. Labeling on the existing sorbent tube range comprised an alphanumeric serial number and Markes branding, but needed to include the serial number in barcode format.

Having a barcode on the sorbent tubes was an essential requirement, as the barcode helps customers reduce errors when recording and tracking samples while eliminating time-consuming manual data entry. The barcode also had to be in Code 128 format (featuring the entire 128 ASCII character set) to provide optimum long-term readability. This particular format is an ultra-high-density linear symbology designed to encode text, numbers and numerous functions.

Switching to Decals

For Markes’ range of stainless steel sampling tubes, the company had always achieved good results by using a laser marking process. However, the company found that the process wasn’t suitable for creating barcodes on the range of glass tubes because it couldn’t make the detailed and clearly defined markings needed. The Markes team therefore set about identifying an alternative process.

“The requirements of this job were very challenging, and any solution had to be precisely tailored to our requirements in order to meet our high standards,” explains Steve Oldfield, Consumables Product manager at Markes International. “Once VOCs have been sampled onto our sorbent tubes, they are analyzed by thermal desorption (i.e., gas chromatography). As part of this process, the tube has to be heated to a high temperature under a flow of inert gas. For some applications, the temperatures can be as high as 400°C.”

The tubes also have a long lifetime (the sorbent inside the tubes can last for up to 200 thermal cycles), so the barcode had to be durable. In addition, the barcode had to be formed on the tube’s relatively small curved surface, but still be easily readable by a handheld scanner.

Markes tested samples from several manufacturers, all of whom applied barcode “labels” designed specifically for high-temperature applications. Unfortunately, these tests found that the labels became smudged and unreadable at prolonged high temperatures. Oldfield and his colleagues next explored the use of high-temperature paints, but the inkjet application process proved problematic and, as with the other methods, it didn’t perform particularly well after being exposed to prolonged high temperatures.

The Ideal Solution

“When we met with the team at Xerital, we straight away found them to be very positive and quick to gain a clear understanding of our requirements,” says Oldfield. “The samples they provided for us were applied using a kiln-fired ceramic decal, and our testing showed these to be extremely good. In particular, the white ceramic background made barcode reading far more reliable than with sorbent tubes from other suppliers, where the barcode had been applied directly on the glass.”

The barcode decals also proved to offer durable, long-lasting quality. They are heated up to 700°C as part of the firing process, so they are more than capable of performing well at the high temperatures reached during laboratory analysis.

“This project at Markes International has turned out to be an excellent demonstration of the advantages of our specialist ceramic decals for glass applications,” says Howard Quinn, Xerital director. “We cooperated very closely to achieve this success, and I feel that, technologically speaking, both we and Markes moved forward as the process took shape. It’s been a pleasure to work with Steve and his team.”

The barcode decals can be applied to new or existing tubes and are particularly useful for large-scale monitoring studies and for labs with significant sorbent tube stock. High-temperature barcodes can be serialized to customers’ required size and code, and subsequently integrated into their existing IT system.

“Our entire stock of glass tubes is now barcoded by Xerital, and their ongoing process improvements have ensured that product quality continues to be of the highest order,” concludes Oldfield. “We are committed to building on our relationship with Xerital and are now exploring innovative ways to introduce color labeling to our range of glass tubes.”

For more information, email howard@xerital.com or visit www.xerital.com.