how many of us have gotten 'burned' by bad emulsion?

[jvanick]

on monday we opened and sensitized a gallon of SP1400... (it's been on our shelf since last october due to us switching to SP1400W for the winter).

We coated a bunch of screens with it 40+, and started putting them on press on wednesday... having all kinds of wierd breakdown issues, pulled out the stouffer strip and found that we were WAY under exposed, so we over cooked at 2 minutes (nearly 3x our standard 40 seconds)... and same deal, stencil break down... exposed one in the sun for 2 minutes (wow is that easy with DTS... ;... same deal...

sensitizing a brand new batch now and will be recoating all the screens... ugh.

I'm going to start writing the date the gallon came into the shop on the bucket so we don't have this happen again.

-- I'm wondering if we got a old bucket last october that was on the very edge of it's useful life, and then since then it's 'timed' out.

[Homer]

we write stock dates on everything... We also number them so we use them in sequential order.


we have had sample quarts do what you are saying, just from sitting so long. who knows how long the supplier had it too...

[Underbase37]

That does suck. We date as well, although I'm not sure it ever gets a chance to sit around long enough to go bad. We have had coated screens sit long enough that they didn't expose correct.

Murphy37

[Colin]

Check with the manufacturer, but sensitized emulsion is like 4-6 weeks MAX.  Any longer and you experience everything mentioned above.

Also, the 1400W is usable all year round.

[jvanick]

this batch was not sensistized until monday  the LOT # tho was X310922...  the 5er of SP1400W I had was listed as X410609  .. guessing that it means the bad batch was from 2013...

Our rep at Murakami told us not to use the SP1400W in the summer due to it getting sticky on the shirt side... which we did experience when the shop got humid last week...  wierd.

[screenprintguy]

Got a sample quart of saati phu, Sample was great, ordered 5er, had lots of problems,  saati rep said it was our fault and we needed To switch all of our chemo to theirs and we'd have no issues.  NOT! Since then, we've never had those issues. Had to be a bad bucket.

[bimmridder]

I have to preface this comment with, It's our own damn fault. We buy emulsion in 55 gallon barrels. We got a new barrel in and my screen guy goes to town coating screens, well over 100. We use a photopolymer, so no mixing. Well the next day we start making screens and they are just washing out. WHAT THE HELL?! I start working back from developing to find the problem. Everything is it should be until I look at the drum....Wrong emulsion was shipped, a dual cure. Our fault for not looking at the barrel and just assuming. Now why couldn't my screen guy dump five gallons of this on the floor? We've had better days, and worse.

[3Deep]

Only had two bad batches of emulsion knock on wood

[jvanick]

The plot thickens...

Today we went in to finish jobs that got backed up due to bad screens on Friday...

all of my 160S screens that were coated with the new batch of SP1400 are failing...  Stouffer strip is showing 9 solid steps... but on the back side of the screen they're soft...  even at 1 minute 40 seconds on the Starlight.

I pulled a 156 mesh that was coated with the SP1400-W, and exposed it to 7 solid steps at 40 seconds... (both sides of the screen were nice and hard).

What gives?

I mixed up a bucket of Chromaline UDC-2 that we have had laying around since last year (expiration date on it says 10/2015, so I'm sure we're still in the good window), and coated some screens... I'll be going in tomorrow to burn some test screens.

I NEED to get to the bottom of this quick as I have a few decently long runs on tuesday and wednesday and can't be having weak screens.

Any and all suggestions are appreciated.

[Frog]

This almost "cross links" to some of this other current thread.

[jvanick]

interestingly it sorta does.. but why the SP1400W would be perfectly fine vs the standard 1400 I have NO idea.... especailly when the standard 1400 was fine before we switched to W

[ABuffington]

As the manufacturer we contacted Jason and have arranged replacement of the diazo and some emulsion.  Sorry for your issues with the emulsion Jason, but it does have a shelf life, especially diazo.  Diazo emulsions once mixed have a shelf life of 4-6 weeks. 

Some Notes on Diazo and Diazo emulsion handling for everyone:

The issue is the diazo had exceeded it's shelf life. Photosensitive products, especially diazo, have a shelf life, we fly ours in bulk from Japan every month and keep it in a freezer.  Several areas can affect diazo emulsions.  Time, Temperature and Moisture.  If you want the longest life from your diazo powder prior to mixing, keep it in a plastic bag in a freezer. Do not use the refrigerator, only the freezer, as refrigeration adds moisture to the inside of the bottle and can cause the diazo to dark harden quickly.  Once diazo is added to emulsion you have 4-6 weeks of optimum sensitivity.  Do not refrigerate the mixed emulsion.  It only increases viscosity and adds water to the bucket every time it is returned to the refrigerator due to moisture forming on the inside of a warm bucket going into a cold storage area which dilutes it.  Just store diazo emulsion below 80 degrees once mixed in as dry an area as possible.  Diazo will 'dark harden' if exposed to high ambient temperatures for long periods of time in the 90's or 100's.  Avoid leaving coated diazo screens for long periods in hot drying cabinets.  An hour is max.  The result of 'dark hardeneing' is when you develop a screen it is hard to wash out the image area and if you are able to wash it out the emulsion edge may sawtooth.

The other area that appears out of nowhere causing customers to think they have a bad batch of emulsion is metal halides can often start losing UV output rapidly toward the end of bulb life.  Integrators mask this aging of the bulb when the unit is set to light units. A good practice is to set your exposure unit to 1 LTU = 1 Second when setting up your system after installing a new bulb.  This way downline you can time 60 LTU.  If the time starts running far longer than 60 seconds you know your bulb is aging.  At some point the exposure unit lamp will not turn off automatcally when set to light units.  This is an indication the bulb has hardly no UV output, although it may strike and still produce white light and a weak image, it will not produce a strong screen.

Finally, 'Bake the Cake'.  Emulsion is very similar to baking bread or a cake, if you shorten the baking time bread will be gooey on the inside.  Same with emulsion, it will be weak and underexposed, you need to bake it as long as you can and still get excellent imagery, not as short as you can.  If you take a white rag during development and wipe the inside of a wet screen you should not see the emulsion color.  If you do just add 10% more time or LTU in increments until you don't see any emulsion color and the image is still holding good resolution.  Always use the blackest positives possible, light colored see through images will require underexposure to get the image.

If anyone has any issues with Murakami Emulsions I'm here to help you get back to where you like it.  Again sorry Jason for the problems you had, we are here to help solve it.

Alan Buffington
Cell: 323.980.0662