PLA (Polylactic Acid) is one of the most popular 3D printing materials thanks to its ease of use and excellent print quality. Despite its many benefits, PLA 3D-printed objects are not food-safe.
Factors like additives, printing equipment, filament manufacturing, and layer lines introduce contaminants and provide a breeding ground for bacteria. By understanding these challenges, you can work to post-process your prints so that they become food-safe.
In this post, we’ll explore what makes a material food safe, the risks of using PLA with food, and how I minimize those risks to create food-safe 3D prints.
What Makes a Material Food Safe?
We consider materials food safe when they meet specific standards, ensuring they do not introduce harmful substances or contaminants into food. Here are the key factors that define food-safe materials:
- Non-Toxic Composition: Food-safe materials must not contain chemicals, additives, or heavy metals that could leach into food. For instance, plastics must be free of harmful substances like BPA or phthalates.
- FDA or Equivalent Certification: Many countries require certification from regulatory bodies like the FDA (Food and Drug Administration) for materials that come into contact with food. The certification process ensures the material has passed stringent tests to verify its safety for food use.
- Resistance to Bacterial Growth: Food-safe materials should not promote bacterial growth. They should have smooth, non-porous surfaces that are easy to clean and sterilize.
- Durability Under Food-Related Conditions: Materials used with food should withstand common food-related conditions, including exposure to moisture, heat, and acidity, without breaking down or releasing harmful substances.
- Clean Manufacturing and Handling: Food-safe materials must be produced and handled in clean environments to avoid contamination with dirt, oils, or other harmful agents.
While PLA can meet some of these requirements, filament manufacturing, and printing make it impossible for PLA-printed objects to meet all of them.
Risks of Using PLA With Food
While 3D-printed PLA has the potential to be food-safe, several risks make it unsuitable for food-related applications without proper precautions. These risks arise from the materials used in PLA production, 3D printer components, and how PLA objects interact with food.
1. PLA Additives May Not Be Food Safe
PLA can be food-safe, but most commercially available PLA filaments include additives such as dyes, fillers, and other chemicals. These additives improve the filament’s color, strength, and printing characteristics, but many aren’t safe for food applications.
If you’re creating products that will contact food, you must use PLA filament labeled as food-safe and manufactured under FDA or similar certifications. Before using PLA filament, you should check the material information and safety data sheet for the brand you’re using to see if there are any non-food-safe additives.
However, even certified PLA filaments may pose risks if not properly printed and handled.
2. Non-Safe Printheads Contaminate Your Print
A 3D printer’s nozzle and printhead can contaminate the PLA during printing. Most 3D printers use brass nozzles, which may contain trace amounts of lead. This lead can transfer to the printed object, making it unsafe for food use.
Even if you use a food-safe nozzle, previous prints with non-food-safe materials (like ABS or PETG) leave a residue that contaminates the PLA.
Additionally, printer hot ends aren’t food-safe. When the filament passes through the extruder, the gears can leech metal into the plastic, and the grease used to lubricate them can enter the print.
You should use a food-safe stainless steel nozzle to reduce this risk. You should also dedicate one printer specifically for food-related prints to avoid cross-contamination.
3. Layer Lines Are a Breeding Ground for Bacteria
The layer-by-layer process of 3D printing creates grooves between layers, known as layer lines. These imperfections are a significant issue when using PLA for food applications.
While 3D prints look and feel smooth and solid, they contain microscopic pores that trap moisture and food particles. Once a 3D-printed PLA item comes into contact with food, the pores can retain particles that lead to potentially harmful bacterial growth.
Further, the layered nature of FDM 3D printing results in grooves between layers where food gets trapped, creating an ideal environment for bacteria to thrive.
Thoroughly cleaning these parts is a significant challenge. PLA’s low melt point means you can’t wash 3D prints in hot water or a dishwasher; otherwise, they will warp and degrade.
These limitations make 3D-printed PLA items unsuitable for repeated food contact. Later, we’ll examine smoothing and applying a food-safe coating to seal the surface.
4. Filament Contamination is Common
Filament contamination is another concern when using PLA for food-related projects. During storage and handling, PLA filaments pick up dust, moisture, and other pollutants.
- Moisture Absorption: PLA is hygroscopic, meaning it absorbs moisture from the air. Wet filament degrades and doesn’t print well, introducing gaps and holes in prints that trap food particles and contaminants.
- Storage and Handling Conditions: Filaments stored in open or dusty environments pick up dust and debris that make their way into the print.
You can minimize contamination risks by storing PLA filaments in airtight, moisture-free containers and using disposable gloves during handling. I recommend printing with an enclosure to prevent dust and moisture absorption during printing.
How to Improve Food Safety
While PLA 3D prints aren’t food-safe, there are some things you can do to improve the food-safety qualities of your 3D-printed objects. Here are some tips to safely use 3D prints for food applications.
1. Choose Food-Safe PLA Filaments
Look for PLA filaments labeled as food-safe and certified by regulatory bodies like the FDA or the EU. Unfortunately, there aren’t many food-safe certified filaments.
If you can’t find a food-safe PLA, choose a filament without added colors, fillers, or performance enhancers.
2. Design and Post-Process for Food Safety
Layer lines and intricate details form crevices that trap food particles and contaminants, creating an ideal environment for bacterial growth. Designing your model with smooth surfaces and sanding it to eliminate layer lines can significantly minimize these problem areas, reducing the risk of contamination.
- Design Smooth Models: Intricate shapes, sharp angles, and hard-to-reach crevices make cleaning difficult and increase the risk of bacterial growth. When designing items intended for food use, prioritize simplicity and smooth surfaces. For example, opt for rounded edges and avoid overly complex patterns or fine details that could trap food particles. If your design includes hard-to-clean areas, consider splitting the object into multiple parts for easier cleaning and reassembly.
- Smooth Surfaces: Sanding and polishing your prints reduces the gaps between layers, minimizing the areas where food can stick. Start with coarse-grit sandpaper to remove larger imperfections and progress to finer grits to achieve a smooth finish. Wet sanding with higher grits (400, 800, and 1200) creates a super-smooth surface while preventing scratches. A smoother surface makes the print safer for food contact and enhances its appearance and usability.
- Seal the Surface: Even after sanding, microscopic pores remain on the surface. A food-safe coating seals these pores, creating an entirely non-porous surface that is more resistant to bacteria and easier to clean. I like to use epoxy resin, which creates a glass-like finish and ensures a completely sealed surface. Similarly, silicone provides a watertight and durable coating that is easier to apply and safer during curing. Regardless of the coating, always ensure it is certified food-safe and follow the manufacturer’s instructions for proper application and curing.
4. Upgrade Your Equipment
Your 3D printer is a significant source of contaminants. It’s best to use a dedicated printer that you only use for 3D prints that come in contact with food. You should only use PLA to avoid cross-contamination with non-safe filament materials.
Additionally, you should upgrade from a brass nozzle to stainless steel, which prevents contaminants from leaching into the print.
5. Be Mindful of Long-Term Use
While food-safe coatings and techniques can make PLA more suitable for food applications, they often degrade over time. Factors like washing, exposure to heat, and regular use can wear down coatings, potentially exposing the porous PLA surface underneath.
You should replace items regularly, especially if you notice signs of wear and tear. Avoid using your prints in high-heat applications.
PLA has a low melting point and will warp and degrade when exposed to hot food. Therefore, avoid using your 3D prints with hot food and drinks, and never place your models in the dishwasher, microwave, or oven.
