[PositiveDave]

It's easy to determine the optimum exposure time for a system even if you don't have an exposure calculator such as the Stouffer strip. Commercial exposure calculators are neutral density filters that allow specific percentages of the light to pass through so that you get a range of exposures from one experiment. This can be achieved in a less elegant but more practical method.
Standardise all your variables:
Thickness of emulsion
Emulsion type
Exposure difference
Temperature

Take a coated screen and cover all but about an inch with a piece of card, expose for a minute.
You may have a good idea what the exposure should be, you can alter the range given in this tutorial to suit your system.

Move the card over an inch and expose for another minute:

After a few minutes you will have a screen with a range of exposure on it:

When washed out it may look something like this:

1&2" have washed out, 3&4" are underexposed, 5" is OK, 6 is probably safe.
If you haven't got a reasonable range, just go back and do it again.
Your light source will deteriorate over time so you should repeat at regular intervals and if signs of underexposure occur.
It will be a good idea to have a positive with some text on to check for overexposure, when the open areas are filling-in you are overexposing.​

 

[gerry]

Thanks Dave, That can save a lot of time and aggravation.

 

[PositiveDave]

It isn't rocket science but I got bored of explaining it three times a week.

 

[splathead]

Hey dave, isn't that last image backwards? #1 has received the most light, so why would the emulsion have washed out?


2/19/10 Update: So as not to confuse new readers of this post, Dave corrected the image, but changed his numbering sequence. In the last image, #1 has received the least light, so the emulsion completely washes out. #8 has received the most light.

 

[PositiveDave]

Correct! I was just testing.

 

[splathead]

Correct! I was just testing.

Hehe. trust me, I got a headache just trying to figure out if I was right or not.

 

[ole Jobe]

Thanks, Dave. I also have a 1" strip of film with 1" squares with 10%-90% halftone dots in 10% increments as well as a solid area. This tells me the dot pattern I can hold on different meshes, coatings. God Bless.

 

[fajaryayat]

so useful tips for beginner like me. thanks...

 

[MotoskinGraphix]

Would it not be better to have some sort of image? Even just a row of square blocks.

 

[PositiveDave]

Would it not be better to have some sort of image? Even just a row of square blocks.

You want the advanced class
It's helpful to have some lines/text to diagnose over-exposure and under cutting problems but you should really get something like an Autotype calculator which has everything on the same small film.
If you get a Stouffer or an Autotype calculator, put it on each screen you make. Your light source deteriorates with age (don't we all).

 

[MotoskinGraphix]

I liken myself to a fine wine and just get better with time!!!!

 

[PositiveDave]

I got corked along the line

 

[out da box]

I dont like the idea of putting am exposure test image on every screen. Every so often, yes. Taping off screens and image areas is a pain and extremely time consuming. The less to tape the better.
Plus once you've got it dialed in, it's dialed in until you change something.

 

[MMACrypt]

tagging for future use, thanks for the info.

 

[red514]

I dont like the idea of putting am exposure test image on every screen. Every so often, yes. Taping off screens and image areas is a pain and extremely time consuming. The less to tape the better.
Plus once you've got it dialed in, it's dialed in until you change something.

true but the test strip isn't very big and is easily covered with a piece of wide masking tape. I haven't experienced this yet but from what i've been reading regarding exposure units, the lamps will degrade over time. i don't think it's that important to use the strips on every screen but at least 1 screen a day. If you do run into issues then use it on every screen until the issue is resolved. I feel these test make a big difference when dealing with fine detail and high mesh counts, for those types of jobs i'd like the strips to be used on every screen.

 

[norbac]

true but the test strip isn't very big and is easily covered with a piece of wide masking tape. I haven't experienced this yet but from what i've been reading regarding exposure units, the lamps will degrade over time. i don't think it's that important to use the strips on every screen but at least 1 screen a day. If you do run into issues then use it on every screen until the issue is resolved. I feel these test make a big difference when dealing with fine detail and high mesh counts, for those types of jobs i'd like the strips to be used on every screen.

Ok, newbie here. So let's say I used a Stouffer or an Autotype calculator, obviously I need to rinse it to see how it washes out. Now my question is, should I just "dry" the rest with a towel or "something", and it will be ready to expose with the art and print right away?, obviously just covering it with tape like you said.

I'd appreciate any advice on the right procedure and or steps, and if possible a good place to get the calculators.

 

[splathead]

Ok, newbie here. So let's say I used a Stouffer or an Autotype calculator, obviously I need to rinse it to see how it washes out. Now my question is, should I just "dry" the rest with a towel or "something", and it will be ready to expose with the art and print right away?, obviously just covering it with tape like you said.

I'd appreciate any advice on the right procedure and or steps, and if possible a good place to get the calculators.

Pat dry with paper towel. Don't rub. Pay special attention to the image. Make sure there is no water film left in the screen. Then let it sit until completely dry. I usually allow about an hour.

The tests can usually be purchased from the same place you buy your screens or emulsion.

 

[norbac]

Pat dry with paper towel. Don't rub. Pay special attention to the image. Make sure there is no water film left in the screen. Then let it sit until completely dry. I usually allow about an hour.

The tests can usually be purchased from the same place you buy your screens or emulsion.

Thanks a lot Splat.
When you say, "pay special attention to the image" what do you mean?.

Just to make sure, the screen I run the test on, is later used for my printing right?. Obviously following your instructions to dry it, and then covering the test results with tape.

 

[splathead]

I mean not to let water dry in the image area. It could be mixed with dissolved emulsion and cause your image to not be as sharp. When you are patting the image down with paper towel, make sure no water whatsoever is left in the image area.

The test strips are placed in a corner of the screen. You would tape them off prior to printing.

 

[norbac]

Thanks again Splat, your help is much appreciated.