Cryogenic and freezer storage for high-value lab samples can pose a challenge. Samples that need to be stored in extreme cold need to be properly and carefully labeled in order to maintain the integrity of the sample, but getting labels to stick in those conditions can be tricky.
Both your tubes and cryo or freezer labels may need to endure liquid nitrogen, temperatures as low as -196 degrees Celsius and lab chemicals. These are extremely harsh environments that some tubes and vials are not prepared to face; let alone the labels and barcodes that are on their external surface.
Due to this challenge, we are often asked the question, “Why are my cryogenic labels falling off?”
As barcode and label experts that specialize in cryogenic storage labeling, we wanted to inform you of three reasons we often encounter to why cryogenic labels may be falling off of your tubes and vials as a result of cryo storage.
Problem #1: The labels are being applied to a frosted surface
Cryogenic labels are meant to withstand extreme cold and frost but, that doesn’t mean they can be applied to any surface. Many cryo labels claim to be able to be applied to frozen samples, and though they may adhere initially, issues may arise later on in your processes if you don’t properly prepare the surface.
When samples are frozen a layer of frost is formed on the surface of the container; while the frost is solid a label can be applied to it, but it’s not a great idea.
When you attach a label to a frosted vial you aren’t applying the label directly to the container, but rather to the frost. This means you essentially have a layer of water between your adhesive label and your sample container, and when this layer melts the adhesive will lose grip potentially causing the label to fall off.
Solution #1: Self-laminating labels
The simple solution to this problem is to wipe the frost from your tube or vial before applying the label. This will remove the water before the sample is returned to cryogenic storage, allowing the label to stick to a dry surface where it’s more likely to adhere.
Another trick is to get cryogenic labels that wrap around the whole tube or vial so the adhesive sticks back onto itself, and doesn’t solely rely on the surface area of the cold container. This increases the chances of permanence, as the label is not solely stuck to the frozen surface.
Problem #2: Your cryo or freezer labels aren’t engineered for your purposes
The way plastic behaves varies with its environment; for example, plastics tend to shrink and stiffen as they freeze. These changes also tend to vary by plastic type, so, some plastics will shrink faster than others even under the same conditions. This means both your labels and your cryo containers will undergo some changes during the storage process, and those changes won’t always be consistent between the two of them.
When labels freeze they naturally want to return to their original flat shape. This becomes an issue when labels are adhered to round sample containers prior to being frozen. As the labels stiffen up they flatten out, occasionally leading their edges to lift from the surface of the tube or vial. This is an even bigger issue with conical tubes and vials with the added curvature of the conical base.
The shrinking of plastic sample containers can also interfere with adhesion. When the container material shrinks more than the label material the label can lift off of the sample, pulling adhesive away from the surface of the container. This can lead to tearing, warping and loss of adhesion.
Solution #2: Source properly engineered labels
It’s a good idea to source your cryo labels from a manufacturer that engineers face stock and adhesive that are both cold resistant and flexible enough to endure such extreme storage requirements. Your supplier may even have options that aren’t pressure sensitive, such as direct mark, so you don’t have to worry about label materials or adhesives at all. At Computype we offer direct mark technology through our label outsourcing program, Ready Labware Services.
You should always ensure your label supplier is familiar with any special conditions your samples will face so they can tailor your labels to your needs if necessary.
Problem #3: You are applying the label to a warm tube
Applying labels to tubes that are too cold isn’t the only time issues arise, in fact applying labels to tubes that are too warm can cause labels to fall off as well. Plastic not only shrinks when frozen, but expands when warm, so when a warm tube is placed in a freezer, it will do a lot more shrinking than a cold or ambient temperature tube.
This means that if you put an ambient temperature label on a warm tube the two will both shrink at the same time but at different rates and for different lengths of time. This can lead to the adhesive being torn from the surface of the sample as one shrinks faster than the other or the tube continues to shrink once the label has completely shrunk.
Solution #3: Wipe the tube clear of frost
A simple solution to this issue is to apply labels to cold samples after wiping them clear of frost. This way as the label shrinks on the vial, the vial will remain the same size and the amount of adhesive affected is minimized.
In cases where the samples must enter storage labeled, look for a labeling strategy that isn’t as easily affected by changes in temperature. In situations like these, we would recommend either a wrap-around label or direct mark technology. Wrap-around labels adhere not only to the container but also to the other side of the label reducing the likelihood of adhesive lifting, while direct mark bypasses adhesives completely and is imaged directly onto the container.
If you’re having trouble with keeping your cryo labels attached, it’s important to take a step back, ensure you’re applying them in a way that ensures optimal performance then consider if you’re using the right labels for your processes. If you consistently see problems reach out to your supplier, explain your processes see if they can offer a better solution.
