A barcode applied by thermal transfer printing technology.

When To Use Direct Thermal vs. Thermal Transfer Labels

Should you use direct thermal vs thermal transfers labels with your labeling machine print engine? That depends on several factors, including material costs, downtime, the environmental conditions of the production area, and the lifespan and physical requirements for your labels. Here’s how each of these factors affects the performance of these printing methods.

What’s the Difference Between These Printing Methods?

Both types of printing technologies use heat-sensitive printing elements. Each element prints one pixel at a time, creating text and images as the label passes through the print engine. The difference between direct thermal and thermal transfer is the way they mark the label.

Direct thermal heats the surface of thermal paper, turning it black. Thermal label printers heat the backing of an ink ribbon until the extreme temperatures cause the ink to melt onto the surface of the label. Both methods are far more reliable than consumer print methods, including ink jet and laser printing, requiring only occasional maintenance relative to the volume of prints. While your office printer may handle a few dozen pages per day, a thermal technology print engine has to handle hundreds of labels every hour across multiple shifts.

How Do These Printing Methods Affect My Choice of Labels?

Direct thermal printers require labels made of thermal paper, the same paper used in receipt printers, and they need a low friction surface to reduce wear on the thermal printhead. While there are low friction coatings, not all coatings reduce friction. Coatings added for other purposes, like UV toner or moisture resistance, can still leave the printed label with an abrasive surface.

Thermal transfer labels need a permeable label surface that can absorb ink. Higher quality labels will pick up ink at lower temperatures. This lets you run the print engine at a lower heat setting, saving wear and tear on the print head. If the ribbon and label are incompatible, the backing can melt onto the label, jamming the printer.

The difference in cost between thermal transfer and direct thermal labels varies widely depending on the application. Direct thermal printing is cost-effective because it doesn’t use ribbons. However, there are specific combinations of performance requirements that can make direct thermal more expensive than the total cost of labels and ribbons for thermal transfer printing.

The biggest difference between thermal transfer labels and direct thermal labels is shelf life. Thermal paper naturally darkens with age, especially if it’s exposed to UV and direct sunlight. Even under the best cold storage conditions, a direct thermal label’s readability lasts for around 6 months. This limits the use of direct thermal prints to shipping labels, perishables and labels for asset tracking.

If you choose to go with thermal transfer printing, you need to consider the ink and label materials for your use case. Ribbons can be divided into three main formulations: wax, resin, and wax/resin hybrids. Wax isn’t scratch or chemical resistant, but it works great with coated paper. It’s best for short term use, like direct thermal printing. Resin has great chemical and scratch resistance, but it only works with plastic labels. The performance of wax/resin ribbons is between these two extremes, while it works on both coated paper and plastic labels. Within these categories, there are several variations, balancing material compatibility, performance and price. For example, Zebra offers 9 types of ribbon, while Sato offers 7 types. If you include third party options, you have dozens of ribbons to choose from.

Can I Only Print in Black?

Thermal paper only turns black when it’s used for printing. While most thermal transfer ribbons are black, some manufacturers offer colored ribbons and metallic inks. However, your print engine will only print in one color, and it can’t vary the intensity of the printed image. For example, if you load the engine with green ribbon, you will only get a solid green print.

How Do Printing Methods Affect Downtime and Print Quality?

One of the advantages of thermal transfer printing is the clarity. In direct thermal printing, the heated printhead wears down as it rubs across the labels. Since the head is out in the open, it can pick up dust and debris. These particles will burn onto the head, causing it to print lines intermittently or skip them altogether. Even when the print head is working correctly, it can’t match the crisp prints of thermal transfer printers. This is important for barcode labels and asset tags, which need clear edges for long-life scannability.

The ribbon used in thermal transfer printing carries dust and debris away as soon as it lands. There are also ribbon backings with low friction coatings, reducing print head wear. This extends the life of the print head, and reduces cleaning requirements. You can expect a thermal transfer head to last at least twice as long as a direct thermal head, and up to four times as long in dusty environments. For example, if the print head has an expected life of 4 million inches using thermal transfer printing, it will print around 650,000 6-inch labels before it needs replacing, which reduces maintenance costs. Switch to direct thermal printing, and that head will only print 160,000-325,000 labels.

While printing is more consistent with thermal transfer labels, it also increases downtime. A standard ribbon is 450 meters long, which is enough to cover a little under 3,000 6-inch labels. If you’re running one of our 3600a Series labelers at full speed, you could be going through a ribbon in as little as 2 ½ hours. On a machine in near-constant use, that equates to 10-15 hours changing ribbons and recalibrating the printer each month. This gives direct thermal printing a clear advantage for maximum output.

What is the Difference Between Print Engines for Direct Thermal and Thermal Transfer Labels?

Most print engines can do both types of printing. In direct thermal mode, they don’t use the built-in reel system for the ribbon. If you know you will only use direct thermal printing, you can save some money by choosing an engine without the reel system. Our print-and-apply labeling machines are compatible with print engines from market leaders: Sato and Zebra. The main difference between these options is their maximum and minimum label printing ranges.

We Can Help You Find the Perfect Labeling Solution

Are you searching for a label printing solution that meets your packaging requirements while minimizing operating costs? CTM Labeling Systems can help Contact us, and we’ll put you in touch with your local distributor. They’ll help you find a labeling machine and print engine that works with your production environment and packaging.