In this article, we’ll:
- What protein glue is and why manufacturers rely on recycled gelatin adhesives
- How recycled gelatin is processed into a high-strength, eco-friendly glue
- The four key phases of protein glue manufacturing
- Why Gram Strength matters when choosing an adhesive
- How sustainable protein-based glues compare to synthetic adhesives
Protein glue—also called jelly glue or recycled gelatin adhesive—is one of the most trusted natural adhesives in modern manufacturing. While synthetic glues have surged in popularity over the last century, protein-based glues have quietly remained essential in industries that require strength, flexibility, and precision, like bookbinding, packaging, rigid box, casemaking, and laminating.
Why has protein glue endured for thousands of years?
Because it delivers something rare: incredible bonding power, clean reversibility, and a manufacturing process that is inherently sustainable.
Today’s manufacturers increasingly seek adhesives that reduce waste and environmental impact. That’s where recycled gelatin shines. Instead of relying on petroleum-based chemistry, protein glue transforms collagen-rich by-products from other industries into a high-performance, zero-waste adhesive.
Below is an inside look at how recycled gelatin is carefully processed into the protein glue used across today’s factories.
Phase I: Preparation - Turning By-Products Into Usable Collagen
Protein glue begins with raw materials rich in collagen. These materials, naturally occurring by-products of the meat and leather industries, are cleaned and refined so nothing goes to waste.
Cleaning and Sorting
Raw collagen-containing material is thoroughly washed, trimmed, and inspected. Removing non-collagen material like fat, minerals, and fibrous debris ensures that only clean, strong collagen continues into processing.
Gentle Conditioning
Next, the collagen is conditioned through a controlled alkaline soak. This step gradually softens the collagen structure and prepares it for extraction. The goal is not aggressive breakdown, but a slow, controlled loosening that preserves the material’s natural strength.
This thoughtful preparation is one of the reasons recycled gelatin adhesives consistently outperform many synthetic alternatives in durability and clarity.
Phase II: Extraction - Transforming Collagen into Gelatin
Extraction is the heart of the process, where collagen is converted into gelatin—the actual adhesive base of protein glue.
Low-Temperature Hydrolysis
Instead of high heat (which could damage the final product), the collagen is warmed gradually in several cycles. Each cycle gently releases a liquid gelatin solution.
- The first extraction produces the highest-quality gelatin with the strongest, longest protein chains.
- Each subsequent extraction uses slightly higher temperatures, yielding larger quantities of gelatin but with shorter chains.
This tiered approach ensures that manufacturers can produce adhesives with tailored Gram Strength, the key measurement that indicates how strong and resilient the glue will be.
Filtration for Clarity
After each extraction, the gelatin solution is filtered to remove even microscopic impurities. The cleaner the solution, the stronger and more consistent the final adhesive.
Phase III: Concentration - Thickening the Gelatin
At this stage, the liquid gelatin is still thin and contains a high percentage of water. To turn it into a workable adhesive, concentration is essential.
Evaporation
Modern facilities use vacuum evaporators to remove water at low temperatures. This is critical—high heat could damage the protein chains that give recycled gelatin its renowned bonding power.
Through careful evaporation, the mixture thickens from a dilute liquid into a syrup-like adhesive base.
Cooling and Gelling
The concentrated liquid is then poured onto cooled conveyor belts or into specialized trays. When the temperature drops, the liquid converts into a rubbery, solid gel. At this stage, it looks like dark gelatin.
Phase IV: Drying and Grading - Preparing the Final Product
The gelled sheets are cut, dried, and inspected in controlled environments.
- Drying chambers ensure the adhesive reaches the ideal moisture content for stability.
- Screening and grading organize the material into consistent sizes and strengths, ready for formulation or shipment.
The result? A clean, strong, highly sustainable adhesive ready to be rehydrated and melted for use across countless industries.
Why Recycled Gelatin Glues Continues to Lead the Way
Recycled gelatin–based protein glue remains a favorite among manufacturers because it offers:
- Exceptional bonding strength
- A naturally sustainable, zero-waste origin Reversibility with heat and water
- Clean machining and easy cleanup
- Long-term durability for packaging, books, laminates, and more
At LD Davis, we’ve spent nearly a century refining and advancing protein-based adhesive manufacturing. While technology continues to evolve, the core principles remain the same: thoughtful preparation, careful temperature control, and the transformation of recycled gelatin into one of the world’s most trusted natural adhesives.
If you’re exploring more sustainable adhesive options for your manufacturing process, browse our blog or explore our full line of eco-friendly glue solutions. Our experts are always here to help.
