Sublimation Printing + Mylar Bags

The sublimation printing community has one cardinal rule; polyester is your best friend. So when we look at a Mylar bag made of PET (part of the polyester family), it would seem to be a match made in heaven. But unfortunately it's just not that simple and getting this wrong will end with melted bags, wasted product, and a heat press with a very unhappy smell.

So let's discuss the actual makeup of Mylar custom food packaging, why traditional sublimation doesn't work on this material, and how using matte Mylar alters the rules.

What is Mylar Exactly?

Mylar is a brand name for BoPET or biaxially oriented polyethylene terephthalate. Mylar is the crinkle metallic film used in many diverse applications such as food wrappers and for insulating space suits.

The qualities that make Mylar so great for packaging food products are also the same qualities that create challenges for sublimation. These include excellent reflectivity/impermeability/heat blocking ability, but not necessarily as heat resistant for heat pressing.

So, Is Sublimation an Effective Way to Print on Mylar Bags?

Sublimation works is by converting dye into a gas, which will then bond with a surface material. In order for it to occur, the material must contain pores or be able to hold onto the dye well enough to allow it to be absorbed.

Polished or metallic foil mylar bags fall short here because the reflective metal coating kept the dye completely on top of the surface, without any way for it to be absorbed, resulting in smearing, washed-out colors, and even warping due to the heat.

Furthermore, when sublimation ink is applied to anything, it is translucent and needs to be on a light or white background in order for the colors to be bright. The very nature of the silver under the surface will cause all the colors to become muddy and pale.

So, the barrier that keeps your food from spoiling also prevents sublimation from functioning correctly.

Matte Mylar: A Better Scenario

Matte Mylar (especially white or very light) bags provide many great benefits. Because they are not reflective, they have a slight texture and many of the matte Mylar bag examples have a higher polyester. This provides more ink acceptance for dye sublimation applications. Here are some comparisons based on the three factors we’re evaluating: 

How to Set up your Matte Mylar Bag for Sublimation

If you are going to try using your matte Mylar bags, here are the best press settings. These settings will give you a softer, less extreme application of heat, allowing you to get enough heat to transfer the dye without damaging the bag.

365ºF Temperature

Lower than Mylar standard.Mylar that has a matte finish cannot withstand more than 400 degrees Fahrenheit without bending or kinking.

Amount of Time Needed

The amount of time needed for this process is between 30 and 45 seconds, so you want to make sure that you do not press for too long; this is the maximum amount of time that you can press your mylar bags together to produce a usable product

Light Use of Pressure

Do not use too much pressure on your mylar bags when applying a printed article to them, as excessive pressure will crush/damage the bags and create an unappealing appearance after they have been printed on. You want to use very little pressure on your bags for this process.

Other Custom Mylar Bag Printing Options

Types of materials that will produce a good-quality image on a packaging style are as follows:

1. Polyester fabric pouches. 

These pouches provide a large variety in size, are easy to work with when printing, and will accept ink the same way that a polyester t-shirt will. The tradeoff is that polyester pouches do not provide a moisture and/or an oxygen barrier like Mylar does.

2. Heat transfer vinyl/HTV applied to Mylar bags. 

You do not need to use a sublimation-ready mylar bag for this method, but it is best for logos, text or small graphic designs.

3. Digital printing / gravure printing mylar bags. 

This application is for those who would like to print wholesale quantities of custom mylar bags; you will receive consistent, long-lasting results, including being able to print on almost all types of packaging.

In Summary

Standard Mylar bags aren’t well suited for sublimation, though it can sometimes work depending on the specific material and finish. Matte Mylar bags tend to perform much better, making them a more suitable option compared to shiny or foil varieties.

Mylar and sublimation printing do not fit well together. By using White Matte Mylar and searching for suppliers who offer Mylar bags with "Sublimation Compatible" advertised, as well as maintaining a conservative temperature during the process, you can successfully sublimate on white matte bags. If you prefer the "Easiest" method when using mylar bags, polyester pouches or applying HTV to mylar bags are still dependable options.