Mill Certificates & Titanium: Why Verification Matters

A detailed guide to understanding mill certificates and why material transparency is essential for safe, reliable body jewelry.

When it comes to body jewelry, not all titanium is created equal. While titanium is known for its strength, lightweight properties, and biocompatibility (non-harmful to living tissue), the differences between standard titanium and F-136 implant-grade titanium can be critical for sensitive ears, new piercings, and long-term wear.

This is where a mill certificate comes in. Our mill certificate verifies the authenticity and quality of the titanium used in all of Grayling's titanium jewelry. Understanding these certifications ensures that the pieces you wear meet the highest safety standards and provide peace of mind. In this guide, we will explain what mill certificates are, why they matter in the body jewelry industry, and how you can use them to make informed purchasing decisions. Bonus: we share our mill certificate.

What is a Mill Certificate?

A mill certificate is a document issued by the manufacturer or an independent testing facility that verifies a specific batch of metal meets certain required standards. It confirms the material's composition, mechanical properties, and traceability, ensuring that the titanium used in your jewelry is authentic and safe. 

While there are other types of certificates, such as general certificates of conformance, an actual mill certificate includes chemical composition, mechanical test results, and heat/lot numbers specific to a material batch. In body jewelry, this distinguishes safe, implant-grade metals from coated alloys or low-quality alternatives. 

Understanding F-136 Implant-Grade Titanium

F-136 titanium, commonly referred to as implant-grade titanium, meets the ASTM F136 standard for medical implants. Its properties make it ideal for body jewelry because it is biocompatible, corrosion-resistant, and extremely low in allergens (ASTM F136 is considered completely nickel-free) Additionally, its strength and durability ensure it can withstand daily wear without compromising comfort or safety.

Unlike commercially pure titanium or other grades, F-136 is specifically tested and certified for medical and implant use. This certification makes it especially suitable for initial piercings and individuals with sensitive skin, offering peace of mind that your jewelry is both safe and long-lasting. It is worth noting that while our PVD Gold finish is suitable for healed piercing locations, only uncoated, high-polish titanium is suitable for fresh piercings.

How to Read a Mill Certificate

A proper mill certificate contains several key elements that verify a titanium batch. These include:

• The name of the testing party
• The material specification (in this case, ASTM F136)
• The heat/lot number
• A chemical composition breakdown
• Mechanical properties test results
• A certification statement
• The testing date

What Mill Certificates Tell Customers

A mill certificate serves as proof that the titanium sold by a manufacturer is authentic F136 and is traceable to its source and compliant with ASTM standards. It reassures customers that their jewelry is safe, biocompatible, and manufactured with care.

As someone who has pierced over 20,000 clients, Blake Perlingieri of Nomad Piercing stresses the importance of this verification process, “The mill certificate tells you if you're actually getting what you think you're getting. So make sure anyone you're buying body jewelry from has a valid mill certificate and that it's legit”.

This simple step ensures transparency, confirms the material’s authenticity, and distinguishes professional-grade jewelry from low-quality alternatives. Transparency in the supply chain is a hallmark of reputable companies, and the presence of a mill certificate is often the first indicator that a brand takes quality and safety seriously. A mill certificate provides peace of mind, ensuring that the jewelry you purchase is reliable, safe, and professionally manufactured. 

What to Look Out For (Mill Certificate Red Flags)

A missing or suspicious mill certificate is a strong warning sign, especially for initial piercings and sensitive skin. Here is a list of red flags to watch for when reviewing a company's mill certificate. 

• Missing or incomplete information
• Certificates that don't specify ASTM F-136
• Vague or generic test data
• No heat/lot number for traceability
• Chemical composition outside acceptable ranges
• Documents from unverified mills
• Photocopied or outdated certificates

Pay close attention to these details, as they can make the difference between safe, high-quality jewelry and low-quality junk. When in doubt, always ask for clarification. A reputable company will provide clear, verifiable answers without hesitation. Staying informed about red flags will help you protect your health and your investment in quality titanium jewelry. 

Why Mill Certificates Matter for Body Jewelry Customers

Understanding mill certificates is about more than the technical details. It directly impacts health, safety, and long-term wearability. Jewelry verified by a mill certificate protects against allergic reactions and skin irritation, ensures durability over time, and supports proper healing for new piercings. As Blake explains, “In my thirty plus years as a professional piercer, implant-grade titanium is the most biocompatible option next to 18k gold." 

Does Grayling Jewelry Have a Titanium Mill Certificate?

Hell yeah! In the Fall of 2025, we had samples of our titanium testing done by independent lab. We included both raw, uncoated titanium and 18-karat PVD gold over titanium for testing. TL;DR: The titanium we use is third-party verified for purity and metal content and exceeds the requirements to be classified as ASTM F136.

We've uploaded the mill certificate below. On page one, you'll notice the area (top left) with the logo from an independent metallurgical engineering firm based in Texas. Next, you'll see two baggies containing samples of our top-selling Mya Hinged Segment Rings (we use the same material for these as we do for our entire titanium earring collection). Finally, take note of the area outlined in green. This notes that the jewelry we sent in met or exceeded standards set forth by the American (now International) Society for Testing and Materials Standard (ASTM). 

While your exact piece was not from the specific batch listed on this paperwork, having documentation about our materials shows we are dedicated to ensuring the quality of every piece of jewelry we offer. 

Thanks for reading!