starlight exposure unit + emulsion type (exposure times)

[tuanoooo]

hey i was wondering if anyone has a starlight unit and would like to share their exposure time. Im new to the industry. I was wondering the exposure time on the emulsions that you are currently using. I just ordered one of these like 4 weeks ago they told me Dec. 1st is the shipment date. Any info would be appreciated!

[Mr Tees!!]

...I have a Starlight. I use CCI WR-14 emulsion (diazo-type), and expose all meshes @ 40 sec. When I first got the Starlight, I was burning at about 25 sec, but I add the extra 15 sec for insurance, in case I decide to run an order with waterbase and/or discharge inks.

...if you are running a Photopolymer emulsion, I have seen times anywhere between 2-12 seconds.

[tuanoooo]

awesome. Thanks Mr. Tees im actually new to all of this so everything is new to me. Also fast question i have very little knowledge about emulsion brands and type. Since you said you are using diazo type. whats the difference between that and just a photopolymer?

[Mr Tees!!]

I'm posting from a phone, which I don't type well on, but here's a good overview:

[url]http://m.youtube.com/watch?v=QUNjF7XB7AM/[url]

Basically, I found the exposure speed of photopolymers (PP as they are sometimes called) to be problematic when exposed with these new LED units. Its very easy to overexpose, and most using PP & LED exposure are using different exposure times for each different mesh counts. For me, its easier to have a slightly longer exposure time and keep it the same across all mesh counts.

Plus, we do some waterbase, discharge, and even solvent/air-dry printing, which PP emulsions will not hold up to.

[tuanoooo]

that is the last thing i want to run into is over exposing. Thanks a lot for the good info! it surely has help me out a lot and decide better on what i will be using!

[244]

that is the last thing i want to run into is over exposing. Thanks a lot for the good info! it surely has help me out a lot and decide better on what i will be using!

Our LED unit will no more expose or over expose your screen than any other type of exposure unit. It should actually be better at getting it right on every time as the light source will not degrade as a Mercury vapor bulb will. Just an FYI

[Gilligan]

I think the point is at 4 seconds there is less latitude for error vs 45 seconds.   If you go half a second longer at 4 seconds then you exposed it 12.5% too long where as with 45 seconds 12.5% is over 5 and a half seconds.

[Frog]

that is the last thing i want to run into is over exposing.

For the last forty years or so, the exact opposite, under exposure, has been at the root of almost all stencil issues. Mostly due to operator error, fear of losing detail, and cutting corners by not using an exposure calculator or manual step wedge test to see exactly how their particular coating technique, different meshes, emulsion, and light source interact.

[Hey Monkey]

I'm posting from a phone, which I don't type well on, but here's a good overview:

[url]http://m.youtube.com/watch?v=QUNjF7XB7AM/[url]

Basically, I found the exposure speed of photopolymers (PP as they are sometimes called) to be problematic when exposed with these new LED units. Its very easy to overexpose, and most using PP & LED exposure are using different exposure times for each different mesh counts. For me, its easier to have a slightly longer exposure time and keep it the same across all mesh counts.

Plus, we do some waterbase, discharge, and even solvent/air-dry printing, which PP emulsions will not hold up to.

Granted I am new to the game but I use Textil PV and only do Waterbase and Discharge. Mind you I am doing lower runs (all manual shop and will stay that way) but not one problem so far. I'll be interested to hear more about PP and LED exposure. I may even get a new LED unit for my new studio.

[244]

I think the point is at 4 seconds there is less latitude for error vs 45 seconds.   If you go half a second longer at 4 seconds then you exposed it 12.5% too long where as with 45 seconds 12.5% is over 5 and a half seconds.

That may be true but the real benefit of LED exposure is once you dial in your exposure time for proper cure it will never change unlike other types of units. To each his own but if I was just starting out I would definitely go LED.

[Frog]

I think the point is at 4 seconds there is less latitude for error vs 45 seconds.   If you go half a second longer at 4 seconds then you exposed it 12.5% too long where as with 45 seconds 12.5% is over 5 and a half seconds.

That may be true but the real benefit of LED exposure is once you dial in your exposure time for proper cure it will never change unlike other types of units. To each his own but if I was just starting out I would definitely go LED.

With the less leeway granted by LED's shorter exposure times, calculating correct times for all various combinations is of even greater importance than before.
I, and I suspect a lot of forum veterans, sincerely hope that a word to the wise is sufficient, and a new generation of screen makers will not necessitate frequent visits here by Step Wedge Man (and of course, Exposure Lad)

[Gilligan]

I think the point is at 4 seconds there is less latitude for error vs 45 seconds.   If you go half a second longer at 4 seconds then you exposed it 12.5% too long where as with 45 seconds 12.5% is over 5 and a half seconds.

That may be true but the real benefit of LED exposure is once you dial in your exposure time for proper cure it will never change unlike other types of units. To each his own but if I was just starting out I would definitely go LED.

With the less leeway granted by LED's shorter exposure times, calculating correct times for all various combinations is of even greater importance than before.
I, and I suspect a lot of forum veterans, sincerely hope that a word to the wise is sufficient, and a new generation of screen makers will not necessitate frequent visits here by Step Wege Man (and of course, Exposure Lad)

Exactly!

[Dottonedan]

Basically, I found the exposure speed of photopolymers (PP as they are sometimes called) to be problematic when exposed with these new LED units. Its very easy to overexpose, and most using PP & LED exposure are using different exposure times for each different mesh counts. For me, its easier to have a slightly longer exposure time and keep it the same across all mesh counts.

Plus, we do some waterbase, discharge, and even solvent/air-dry printing, which PP emulsions will not hold up to for different reasons.

That is the beauty of this industry. There are not many (exact or "right" ways) to do things for your shop. What works great for one shop, another would not touch for different reasons.

Some shops like you said, use a PP with a tight window or room for error (and they then, must have a different exposure time for each mesh (to have that mesh exposed optimally). Even more time is needed, for those who coat differently for different mesh. Thicker coats (e.g) 2:1 with a round edge coater) can increase exposure time slightly versus a 2:1 with a sharp edge coater and even faster exp. times for those who coat 1:1 using a round versus someone who uses 1:1 using a sharp.

Each PP emulsion brand can have different (lengths) of proper exposure times depending on their chemical makeup. Some faster and some slower than other PP's. Some work for one shop and others work for another shop (for different reasons). It might be something like price, edge definition, production durability, or even color.

When you jump to a dual cure, or a different PP with even a longer exposure window (aka a hybrid emulsion) you have more opportunity (like you said), to use one exposure time across the board or across all mesh counts.

AS far as I can remember, the only real benefit of having one exposure time, is to streamline your process so that you or your employee never needs to remember if they changed the exposure time for a different mesh. (as far as I can recall).

It can become a choice of cost versus convenience in many cases. In general, I understand the use of a dual cure is dictated by the quantity of your orders (72 or 7200) and also the ink types (waterbase or plastisol).

Emulsion types (PP or DC) or choices of exposure methods can all be excellent choices on an LED unit with much faster times than non LED.

[Frog]

I'm posting from a phone, which I don't type well on, but here's a good overview:

[url]http://m.youtube.com/watch?v=QUNjF7XB7AM/[url]

Basically, I found the exposure speed of photopolymers (PP as they are sometimes called) to be problematic when exposed with these new LED units. Its very easy to overexpose, and most using PP & LED exposure are using different exposure times for each different mesh counts. For me, its easier to have a slightly longer exposure time and keep it the same across all mesh counts.

Plus, we do some waterbase, discharge, and even solvent/air-dry printing, which PP emulsions will not hold up to.

Do you know for a fact that you have exposed all of your mehes at their optimal times (verified with an exposure calculator) or did they just "work"?
While I understand the concept of emulsions with a wider latitude, I still can't believe that we'll get the same results with the same times on everything from a 110 to a 305.
Now, if you are only running 260's and 305's or some similar range, that's different, but I would still wonder if they are doing the best they could.

[Dottonedan]

For those whom I've seen using one exp time, it's more like one exp time for high mesh and one for lower mesh. So a total of two typically, but maybe they don't use that many low mesh, so they often refer to having one exposure time (and occasionally) use another if they have to kind of thing. I can't say for all shops tho.


In those cases, I'm sure the 305 is usable, as is the 156 exposed at the same times, but one mesh will be exposed more accurately, (will hold up to long production runs and also holding the best detail) That would typically be the mesh in the middle like a 230. It's a more appropriate exposure than the higher mesh and the lower mesh (but all may fall within the window of usability).