![]() So, as a first test, you could use a test design, for example, a page of uniform text. The test strip will tell you not only which time is enough to harden the emulsion, but also if the design gets too hard to wash because the borders of the design, especially on thin lines got also burned. You can now test X to 5X time and see which exposure works best for your combination of exposure, light intensity, light distance, temperature, and other variables. ![]() Let's say 5 mins.Īfter time X, uncover 20% more. 20% will be exposed.Įxpose X amount of time. The first step would be reading the instructions for the product.īut on your specific setup, you can do a test strip.Ĭover for example 80% of the area of the emulsion (and design) with thick flat cardboard (It is better if it is painted black on the side of contact) and put some weight on it. ![]() I am assuming the emulsion actually works. The only way to know is that you make a controlled test. It is simply a variation of the times, especially if you are working with an emulsion where you do not have a base idea on how it is the exposure time. I realize this overall answer was explained by JohnB. 4 itentical strips of artwork with the before mentioned details on it, dots, lines and open area. Move the card board over every minute and a half. Invest in an artwork with everything on it.a strip and duplicate that strip 4 times across the screen. It may require moving the light source to and from the image area on your 2nd screen. Don't put the light too close, because the closer you are the more exposure also. Also use different size lines like 1 point up to 10 points in size, this way you can determine if you're exposing properly for small details. See if you can use different types of images, like a block, of course, a gradient of dots from small 10% to 100% open area for small detail. Right this time and distance down, so you don't have to waste screens doing it again. If you get results with less or more exposure time there will not be consistency in other screen exposures. You're looking for an exposure time of approximately 4-7 minutes. 3rd screen is a final adjustment for detail factors. The 1st is a basic setting (course adjustment providing you were too close with light or not close enough). YOu're not using controls so don't worry about a calibration strip. You can do just as the gentleman said with cardboard or something that will totally block the light. I am certainly not an expert on LED lights, but as far as I know they do not emit UV light at all. You say it is an LED light equivalent to a 450W - 500W incandescent light, but are you absolutely certain it can be used to burn a screen? Remember, emulsion reacts to UV light. This method does unfortunately waste a screen, but hopefully you have the equipment to re-coat it yourself. I washed out the screen to find which exposure time produced the cleanest result. Once the screen was fully covered by the cardboard, the test was complete. Every 30 seconds, I would cover another inch of the emulsion by sliding the cardboard forward. I then covered about an inch of the emulsion with the cardboard. I started by burning the whole screen for about 7 minutes. I have used a piece of thick cardboard in the past to test exposure time. You say you don't have a step wedge, but you don't really need one. The best way for you to find out is to test yourself. Burn time can depend on the type of emulsion, mesh count of the screen, exposure light, your film medium (transparency? paper & mineral oil? vellum?), and your exposure setup. ![]() There are far too many variables involved with burning the screen for anyone to give you an accurate answer.
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