Stouffer Scale

The Stouffer Scale: A Sign Maker’s Best Friend


Ensuring ADA compliance is a must for all signage fabricators and manufacturers; however, it’s not uncommon for certain details to slip your mind from time to time. In our experience, one of the most common mistakes in photopolymer production is not making use of the Stouffer Scale to ensure that bulbs are working properly. This might seem like a minor detail but it makes all the difference, considering poor exposure can lead to non-compliance as well as failures causing expensive remakes and loss of customer confidence.

What is the Stouffer Scale?

The Stouffer Scale is a small strip of reusable film negative with a series of numbers on it, ranging from 1 to 21. Each number is encompassed in a block that has different grayscale tones ranging from clear to light gray to black. The Stouffer Scale is considered the “holy grail” of photopolymer processing because it ensures that photopolymer has been exposed properly with correct shoulders ensuring ADA compliance. Like any film negative, the Stouffer Scale reacts to UV light. Continued use of the Stouffer Scale results in lower opacities which causes it to give false readings.

Stouffer ScaleThe Stouffer Scale measures the UV output from the bulbs so that you know when to increase the amount of exposure time to maintain the proper shoulder on the photopolymer. Depending on the results, fabricators will be able to determine when they need to change the UV output by increasing the exposure time or replacing their bulbs. If you detect an irregularity through the scale, your bulbs may no longer be in perfect condition. To ensure your bulbs are working at their best, fabricators must use the Stouffer Scale on a weekly basis. Make sure to record the results in a production log to keep track.


The Stouffer Scale reads different measurements for each type of photopolymer material used. There is not one general fixed value to pinpoint or watch. Each type of material has its own ideal value to reach to show whether it is properly exposed to the right amount of UV light:

It is important for fabricators to know how to properly read the Stouffer Scale. Make sure to read it based on the last exposed number as that number will be the amount of exposure your bulbs are currently outputting. Partial reads should not be considered. If you do not reach the intended exposed number, you must increase or decrease the exposure time or completely change your bulbs.

Shelf Life

Generally, the Stouffer Scale has a shelf life of 1 to 3 years depending on its usage. Its photoreactive nature will change with time, so a scale that has spent more than 3 years in storage won’t work as reliably as a brand new scale. If you are constantly using the same scale, make sure to replace the scale every 6 months to one year, depending on use, to ensure you are getting the most accurate results.

Now, you may be thinking: “That seems like a hassle.” Acquiring a new scale will allow you to continuously create ADA-compliant signage. It is easy to keep using the same scale; however, one small mistake in compliance and exposure can lead to disaster. Think about partnering with a signage manufacturer that can send you a new scale annually. This not only allows you to reduce costs but also guarantees that you are using the most up-to-date scale.


How to Use the Stouffer Scale

Wondering how to use the Stouffer Scale? All you need to do is follow these 8 easy steps. When done correctly, ADA compliance is easily attainable.

  1. Place the Stouffer Scale on the surface of the photopolymer right next to a film negative. This will show you the relationship between the exposure to the shoulder of the photopolymer.
  2. Place the Stouffer Scale emulsion side down so that it shows the right reading.
  3. Center both the photopolymer and Stouffer Scale on the machine.
  4. Ensure a proper vacuum and close the drawer; you can now start the exposure process.
  5. When exposure ends, open the drawer and roll back the vacuum sheet.
  6. Start the washout process.
  7. Once the washout process is complete, place the sheet in the dryer.
  8. After drying and post-exposure, take a look at the results.*

*You will be able to see the scale and the number to which it is exposed. Anything under a solid 15 to 16 will require more UV exposure. Over a solid 16, UV exposure can be reduced.

How to Maintain the Quality of your Stouffer Scale

Production LogAlthough the Stouffer Scale is a fairly simple tool to use, it can get confusing when keeping track of its usage and wear. Fabricators should continuously monitor how well their Stouffer Scale is working by maintaining a photopolymer production log. A production log should incorporate all key items such as dates, job numbers/descriptions, materials processed, lot numbers, exposure times, washout times, wash temperatures, drying temperatures, post-exposure times, and UV scale readings. Keeping track of all these factors allows fabricators to determine how much the scale has been used and when it is time for a scale replacement. Not only does this log provide clear and concise information on the overall usage of the Stouffer Scale, but it also helps to ensure the production of ADA-compliant signage.

Key Takeaways

ADA compliance is the one thing all signage manufacturers and fabricators strive for. Although there are multiple tools and equipment that can help achieve compliance, there is no more reliable ally than the Stouffer Scale. With this in mind, businesses should take the time to evaluate their current workflow processes to stay compliant with the ADA specifications. Those who can properly utilize the Stouffer Scale will not only be able to maintain compliance but also consistently produce the most high-quality signage. Nova Polymers has the ability to deliver custom solutions by providing all the tools you need to ensure ADA compliance. For more information on our services, reach out to us today.

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