Protein glue, or animal glue, is an adhesive typically made from animal gelatin protein. It is also sometimes called “cake glue” in reference to its appearance in 9-10lb blocks after production To ensure protein glue remains a non-toxic and sustainable product, other raw materials, like water, Epsom salts, corn sugar, and glycerin, are added to the gelatin.
Used most commonly in bookbinding, box making, and lamination applications, protein glue is often applied using a wheel, roller, or application pad. Due to its raw ingredients and the nature of how it is applied when protein glue runs too thick or too thin, it can create a frustrating and often messy issue on your production line.
Troubleshooting why your glue might be running too thin or too thick is essential to efficiency and product quality. To do that, it’s important to understand protein glue viscosity.
Viscosity measures a fluid’s resistance to gradual deformation by shear or tensile stress. When it comes to glue, it is related directly to how thick or thin your adhesive is.
Maintaining proper viscosity is necessary for consistently applying your protein glue. Since protein glue is made from common raw and natural materials, understanding the role of temperature and water content in controlling glue viscosity is required.
Temperature is a significant factor in maintaining the right viscosity in your protein glue. As temperature increases, viscosity decreases, meaning warmer glue flows more easily. On the other hand, as temperature decreases, viscosity increases, causing the glue to flow more slowly.
It’s possible to adjust the viscosity of protein glue by adding water, but too much water (or too little) can also cause issues with controlling glue viscosity. Determining whether your glue is too thick or too thin is the first step to troubleshooting issues with glue viscosity.
When your glue is running too thin, the consistency of the glue seems watery or runny. This can make applying difficult and cause the glue formula to fail. Some signs that your glue is running too thin are:
Protein glue that is running too thick may appear too viscous. This means that the glue is not flowing smoothly, may appear sticky, and will often be challenging to apply evenly. This can impact the glue’s ability to bond correctly, and uneven distribution can create trouble in your product's performance.
Determining the causes of your glue running too thick can help you troubleshoot. Some causes to watch out for are:
Maintaining your protein glue at the right temperature ensures its performance. Temperature directly impacts the viscosity and adhesive ability of the glue. When protein glue is at the right temperature, its raw materials can form stronger bonds.
Protein glue is designed to be maintained at a temperature of 140-150°F or 60-65°C. If protein glue is kept at a higher temperature than that, you run the risk of burning it. However, keeping your glue at a temperature below that temperature can cause the glue to become too thick to apply and make it set too quickly.
Troubleshooting your glue’s viscosity issue depends on whether your glue is running too thin or too thick.
There are a few easy fixes to correct glue viscosity issues, whether running too thick or too thin. We’ve assembled two troubleshooting videos to help you determine the cause of your glue’s viscosity issues.
It doesn’t always have to be an estimation game. Using a MIL Depth Gauge before application allows operators to measure glue exactly, ensuring that your glue is always at the proper viscosity. Checking your protein glue’s Technical Data Sheet (TDS) can also ensure you properly heat and dilute your glue.
Whether your glue is running too thick or too thin, troubleshooting the root cause and following these protein glue best practices can protect your production line and its performance from issues related to runny, messy, sticky, or hard-to-apply adhesives.
At LD Davis, we understand that not every manufacturer is the same. If these troubleshooting tips don’t work, there are other solutions. Reach out to us for a technical review or a free glue assessment. Our experts are here to help.