I was reading the post on the archival qualities of regular inks (TW) and latex. I'm no scientist, but here's the way I understand it.
The most important part is the paper....if it isn't 100% rag (made with cotton) acid free, then the chemicals in it will attack both the ink and yellow the paper over time. Some paper companies sell cellulose based paper (made with trees, this is how 99% of regular paper is made) that is acid free - this is very popular with the 'offset litho limited edition'crowd. There is also mixed papers, part rag part cellulose. If you print on regular papers, even without light hitting the piece paper will start leaching colour and turning yellow. It's the air reacting with the chemicals and acids still in the paper. So if you are printing art for the ages, you need to consider your paper. To collectors of art and galleries, this becomes very important. On the other hand, if a particular print is rare, it is rare, and the way it was made is moot.
The second most important part is the printing process. Screen printing lays down a much thicker layer of ink and the ground-up pigments screen ink carries to make colour are more plentiful. It is this thick layer, and the makeup of the ink (pigments and carrier, this is the clear resin binder that holds the pigments together) that determine the ink's light fastness and resistance to fading or discolouring. A layer of offset ink is very thin, and the pigment content very low compared to a similar layer of screen ink. These pigments fade very quickly when exposed to light, and so the amount and thickness of the pigmentation is important for archival puposes. this is why screen printing is so good as aprint process when long life is important, in art prints or just in the world - outdoor signage, etc.
The knock against inkjet prints (giclees) is related to the ink's ability to last and not fade, due to the very thin layer put down on the paper - it's very fine detail at ultra high resolution is due in part to the highly ground pigments and small amounts of actual ink that is forced through the jets. The absence of a thicker layer of binder or resin is also a problem. Some are better than they were a few years ago, but all we have as evidence is accelerated lab testing - the process is so young we won't know how it really looks 10 or 20 years from now.
When we start wondering about the difference between various inks in screenprinting, we have to take it all with a grain or two of salt. Accelerated testing has only been available for a few years, even for screenprinting. Some inks are better than others only because we know they cover and print better, and the pigments are ground finer - clogged screens are a good indication the pigments are larger and hanging up on the screens over a run. There's a reason why paint is cheaper than specialized screen ink. The effort and expense to grind the pigments, and the quantitiy of pigments (finer grind = more pigments used) Cheaper screen inks are like that too, with less pigments in larger sizes.
The inks that were used to print expensive and rare prints by artists in the 40's, 50's, 60's and 70's were mostly pretty crude - enamels and satin posters. Are they archival? Who knows, they were commercial grade and what was available.
So the bottom line is use the best material you can, and be aware of what you are using, and the relative merits of it. If you can't afford archival material, fuck it, keep printing, whatever way you can. Eventually you will be able to use better materials, and you can charge more. They didn't have a clue about archival stuff 100 years ago, they just did it the best they could. You don't see museums throwing out Rembrant or Warhol prints because they used shitty ink.
I try to use the better stuff and it just makes such a big difference. I understand why alot of people use other stuff but at some point they will find out that the better the Ink and paper the better the print.
But hey if it works for you then go for it.