Did you need to buy float (plate) glass that is "stone free" and "optically clear" ...

No...

You do not want to use safety glass (look at the side do you see three sandwich type layers?) - it is too expensive and safety glass is the worst choice, it will always have UV blocking layers.

Regular float/plate glass that is not tempered is what is used in most exposure units now, no need to ask for "stone free" (stone - an inclusion or contaminate in the glass) as most regular glass is 95 plus stone free now anyway!

If you look at the side of the glass you will see a slight "green like" tint - this is normal for standard float type of glass and is caused by Iron in the mixing process this iron in the glass will cause 14 to 17 % loss of UV for each 1/4 inch (or higher) - this is also normal and is caused by the iron content.

The "optically clear glass" is often 3 to 10 times more expensive, and it will also block some UV light (about 1/3 what regular will)!

Some glass is made with more UV block and tends to have a darker green tint and is used for building window glass your supplier could have used a scrap of this that they could just cut to miss a flaw - it is also more expensive so unless you asked for it they would send out the less expensive stuff.

Thicker the stronger, also the thicker the more UV is blocked.

The simple act of tempering the glass DOES NOT change the light transmitting qualities - NOT ONE BIT! (that is an old screen printer myth) - but if the glass is "safety glass" or UV window glass the additives and composition change the UV transition, but safety glass and tempered are not the same thing.

There is always confusion with tempered glass and safety glass - but they are two different types of glass product.

So inexpensive glass will have some UV block (green tint) it is not a coating but IN the glass not laminated sections.

A high end high quality press will cost much more than you may think at first, or a lot less than you expect, depending on what level your entry point.

Shoestring "bottom of the barrel scraper" - "man thats expensive".

Successful business operator - "thats all, wow".

There are lots of entry level presses and for the most part they do the job (some better than others) but the cost reflects a lack of features, an often frustrating lack of features.

Those features may not seem like much now but as you start working to make money (you know - that profit thing) you will find that the frustration and time taken to work without "features" would have paid for a high end press very quickly.

I have heard and seen some printers (and want to be printers) lament, why is there no "reasonable price" good equipment, well because they, like you, need to make enough profit to stay in business.

Good stuff takes expensive parts and trained labor. Many people who cannot understand the idea of "business for profit" may possibly need to rethink getting into the screen printing business.

All of the high end press manufacturers LOVE entry level and old used equipment, particularly presses, because newbies get started in the business with this inferior equipment. The high failure numbers in our industry quickly filters out the folks who are not going to make it, or lack interest or ability. What printers are left will start looking for the features that make the process more efficient. Past pain and frustration will make the experienced and knowledgeable printer pass up the multitude of mid level equipment and almost to the last person, go immediately to the high end equipment!

Some things you can "skimp on" to start with, and many things you can make yourself, but there is a reason that professionals use quality tools, in any industry.

Can an experienced user make the entry level stuff work, yes, in many cases they can even do a better job than a hack with mid to high end equipment, but they will be hampered by using that equipment and that will cost time and profit.

Many of the "slob shop - beat 'em on price" type shop owners I see are stuck in the "olde dayz" where they gained a basic competency and then just stopped, moving into a holding pattern for 15 of the 20 years in business. They can run a business but often that translates into becoming a slave-driver. Somewhere in the last decade they lost or never seemed to learn that to make money you have to spend money.

There seems to be a point where small business owners gain a position in their area where they concern themselves with the "low price leader" mentality and turn inward where they want to squeeze that turnip until they get blood. They never come to understand that in many cases (because they have stunted their learning) they are spending more money trying to squeeze the turnip than they could make with even small expenditures on reasonable or necessary changes.

That is why the truly good and talented float to the top and the mediocre, well they stay that way. I am not saying that you cannot make money with mediocre (Wal-mart, Microsoft, US Auto makers) you can (especially if you understand marketing) but it will eventually cause a loss or failure.

An example, there is one printer I know well where they REFUSE to update the old, huge exposing units and expose the screens completely (they underexpose, because it "takes too long" with the old weak units they have.

This shop has three full-time employees that do nothing but touch up pinholes all day! Three full time workers! To fix a problem that could be completely eliminated with cleaner procedures and on each screen a full exposure!

They could take the money expended each year on the "pinhole-blockers" to buy three, faster, self contained exposing units that would expose fully in less than HALF the time - for less than half of what it cost in pinhole-paychecks! They are always behind in production (no surprise) and even could take a bit of money, buy three new manual presses (or even a small auto) and teach the "pinhole-blockers" to print and increase the shop output!

Rational logic is too rare!

I have to throw in a pitch for our friends over at Graphic Elephants...

A team of what will prove to be the new "go to" guys for high-end help in your shop.

Lon Winters, Jason Ballash, Ken Konnerup from the Colorado based company Graphic Elephants.

Graphic Elephants

Measurable UV production from High Output fluorescent lamps is about 3000 10000 total hours. High Output fluorescent lamps have a long relatively gentile curve of degradation of actinic (chemical reactive) light in comparison to other higher volume lamps (like metal halide).

Unfiltered black light lamps are best for exposure - they give off more actinic light vs. the "filtered" blacklight lamps that are the dark purple color (that tube is actually made of an expensive colored glass called wood's glass).

Unfiltered black light lamps will be single phosphor or low variance europium-doped strontium fluoroborate (in combination with the mercury electric discharge) in contrast to high variance content doped phosphors in "regular" lamps - basically fewer "things inside" to make light that looks "more natural" so everyone does not look like the set from the living dead - in our case we don't care about the visual light spectrum as much as we need the actinic light...

Unfiltered black light lamps when frequently switched on and off (as we will using them to expose, will artificially lower the expected life, so we go from an example of 5000 hours to less than 800 hours.

While much slower and more gradual in loss of output (higher power the shorter the life BTW) fluorescent lamps do degrade and loose output - strangely this is caused by the glass bulb part of the lamp absorbing the mercury from the inside. Sadly for us the loss of output is fastest in the light range needed to expose screens!

There is also a strange thing that happens with emulsions, depending on the type of emulsion when using some dual sensitized emulsions that are pre-sensitized (a "dual cure - SBQ") emulsions the exposure times are excessive with the lower power fluorescent lamps when compared with even a relatively slow to expose diazo-dual cure.

Something about the light reactive chemistry and the output power - all I can post at the moment is that I can put one of the dual sensitized emulsions on a fluorescent lamp exposing unit and the times will be as long or longer than a diazo dual cure and when you take the same emulsions and expose them on a metal halide unit the diazo emulsion will take longer to expose...

On a side note, the smaller the diameter of the glass bulb the higher the output of light per length, thus the skinnier the lamp the "hotter" it will be, they also have a shorter life per length...