# Stouffer 21 step sensitivity exposure guides and how to use them



## Mike Caliper (Oct 11, 2009)

There are several good threads on how to get the proper exposure for your screen frame, your screen mesh, using your emulsion, your coating method, your exposure, etc, using your system and set up at your location. A search of this forum will lead you to that information.

The easy way is the Stouffer exposure guide which can be purchased from Stouffer Graphic Arts Equipment Co., Mishasaka, In, 46544, for less $9.00 Get one and be happy.

Remove the exposure guide from the protective envelope and handle it by the edges to keep it clean. Lay the exposure guide on the emulsion, in a location that it will not interfere with the image. Expose your screen and return the exposure guide to the protective envelope. Wash out the screen as you normally do and look to see the number of the last solid band on the scale.

Usually a solid #7 is the target exposure.

To increase multiply the original exposure time by the following:
1 step, multiply by 1.4 
2 steps multiply by 2.0
3 steps multiply by 2.8
4 steps multiply by 4.0 

To decrease multiply the original exposure time by the following:
1 step, multiply by .70 
2 steps multiply by .50
3 steps multiply by .35
4 steps multiply by .25

To confirm your new exposure time is correct you will need to burn another screen with the the exposure guide on the emulsion, in a location that it will not interfere with the image. 

Expose your screen using the new calculated exposure time. Return the exposure guide to the protective envelope. Wash out the screen as you normally do and look to see the number of the last solid band on the scale.

There are reason for exposing your screens for numbers other than a solid #7, but that is for another discussion. We are trying to get a good solid #7 for a starting point for a workable exposure for your system and your set up.

There are other ways to work toward a good exposure time. Click here for directions on how to make a strip exposure. 

Remember that if you change emulsion, change coating methods, change screen mesh (size or color), change exposure units or bulbs, etc, this can change the exposure time. It is easy adjust for these changes, just place the Stouffer exposure guide on the next screen you expose. Look to see if the exposure time needs adjusted, and make any needed exposure calculations. 

To use the screen, just tape off the area where the exposure unit was placed.


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## Blackwater (Feb 9, 2010)

I just got my scale today. I exposed 2 screens tonight. I am at #4
Thank you for this post because I did not know what # number I was trying to hit.


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## BroJames (Jul 8, 2008)

Mike Caliper said:


> There are several good threads on how to get the proper exposure . . .
> 
> The easy way is the Stouffer exposure guide which can be purchased from Stouffer Graphic Arts Equipment Co., Mishasaka, In, 46544, for less $9.00 *Get one and be happy*. . .
> 
> There are reason for exposing your screens for numbers other than a solid #7, but that is for another discussion. We are trying to get *a good solid #7 for a starting point for a workable exposure for your system* and your set up...


I would say that my exposures are workable enough, although underexposed if benchmarked against the stouffer 21 solid step 7 test. Based on comparative data available in this forum, a great majority of screens seems to be underexposed. I am sold on the stouffer as the standard for determining the best exposure time so I just remitted funds for a Stouffer 21 today but that's where the good news end.

Shipping to the Philippines is $80 by courier so I chose Priority Mail for $14. Western Union charged about $16.50(cancelled my card years ago). Now, I am regretting why I did not use my sister's credit card and ordered 2 more stouffer 21 which would still turn out cheaper. Anyway, shipping and transaction costs, aside from the stouffer, is $30.50 or 4.6 times more than the cost of the stouffer itself. The remaining suspense is how much post office here would charge me. A single stouffer costs a buyer here at least $37.05 or almost 6 day's salary of a minimum wage earner here. $21 if he/she uses a card.

Now that I got one, or am about to receive one, I hope I can still realize the "be happy" part considering the high cost of obtaining a stouffer here. However, this guide better be good. 

However, I am pretty sure that a solid step 7 represents the best exposure time but I am also pretty sure that it is not the starting point for a "workable" exposure. Based on the exposure times that I read here to get a solid 7 on the Stouffer 21, and the actual exposure times that I use, a solid step 3-5 seems to be the starting point for a workable exposure. I guess I will find that out soon. 

And Mike, I am just joking about the "be happy" thing. Thanks. I expect the stouffer to be particularly useful as my UV bulb gets weaker.


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## BroJames (Jul 8, 2008)

Just an update. Based on my regular exposure time I got a solid 5 to 6 on the stouffer. 5.25 to 5.5 if you will. I have upped my exposure time accordingly by about 75%. Based on the exposure times I often heard, I am guessing that a stouffer 4-5 exposure is prevalent and has been accepted by many as OK.


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## VinylHanger (Jul 16, 2010)

I used mine the other day and ended up with a 5. That was with a 7 minute exposure. So it looks like I need to go to 14 minutes? Seems like a big jump when 6.5 minutes has been working pretty well. I suppose I'll try a 14 minute exposure and see what happens. I have dark positives, so there should be no risk of overexposure.


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## DaveG (Aug 3, 2009)

BroJames said:


> Based on the exposure times I often heard, I am guessing that a stouffer 4-5 exposure is prevalent and has been accepted by many as OK.


A screen exposed to a 4-6 on the scale will still print fine, (and in fact will yield more detail on fine halftones and indexed prints), but will not last as long as a screen that's been exposed to a 7 (or 8 for simple spot color). It won't matter for a 20-50 image run, but for certain you'll begin to wear through the emulsion at the edges of your squeegee on a 200 image run!

DaveG


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## BroJames (Jul 8, 2008)

I guess that is why "proper" exposure time varies widely. 

I don't use hardeners and am curious how many people use them in the US.


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## DaveG (Aug 3, 2009)

I don't think there is such a thing as "proper", step 7 is just a starting point. Since there's no question that manual printing is more of an art than a science, it's all about personal preferences and what works with each individual's capabilities, equipment, printing style, and desired end result.

I don't use hardeners either, but I do post harden in the sun (gotta love California weather), and if setting up for a huge run, I'll put an extra coat of emulsion on the screen, and tape the underside of the screen to prevent pinholes at the squeegee edges. 

DaveG


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## BroJames (Jul 8, 2008)

Yes, "proper" is relative to an individual's *"*_capabilities, equipment, printing style, and __desired end result_*"* and that is why it varies widely. As you posted, underexposure _"in fact will yield more detail on fine halftones and indexed prints ...It won't matter for a 20-50 image run_".


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## tpitman (Jul 30, 2007)

As a rule I set my screens out in the direct sun for 15 minutes or so after exposure. It can only help with durability, not to mention increasing the chance of a successful reclaim. Full exposure of the emulsion can eliminate a host of problems.
Use the stouffer scale with every exposure. It'll alert you to creeping issues like bulb age or emulsion expiration, instead of leaving you scratching your head wondering why something that seemed to work before is going wrong. The more variables you eliminate, the easier it is to troubleshoot. Also, make sure you place the scale ON you film or vellum where it's clear, not just on the emulsion. Makes a difference.


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