Archival photo paper is a term used to define the longevity of a photograph or image on a photo paper. In other words, it is a measurement of how long the image will last without losing its colour and without fading or changing its tones. There are three parameters that will directly influence the archival potential of the paper.
The Archival Base Paper
All photo papers are produced on a base paper. Certain chemicals are added to the base paper at the production stage. These chemicals include acids that are added to the pulp mix in order to achieve the desired whiteness you see.
These acids have an adverse affect on the paper in that over time they cause the paper to yellow when exposed to air. In order to produce a solid archival photo paper an acid free base paper is needed so no yellowing will occur over time.
The Archival Coating
The coating of the photo paper plays an important part in the potential of the print to stand the test of time. The coating or receiving layer in its technical description is added to the paper to ensure that the ink is absorb as accurate as possible without occurring any bleeding whilst retaining a vibrant and clear image representing all the colours and the sub tones that the original image printed.
The problem is that these chemicals themselves are still active and with time may attack the colours on the print causing the image to fade even without being exposed to air or sunlight. The chemicals used on the archival photo paper need not only keep the image clear and crisp over time and keep it from fading, but on top of that they should not act against the colours as time goes by.
In inkjet coating there are two main chemicals used to create the coating, one is Silica and the other is Alumina. The Silica is the cheaper of the two and does not equal the archival properties of the Alumina chemical. Using Alumina will increase the cost of the paper but will achieve better archival results though both may produce same image quality at the moment of printing. Remember, we are comparing future credibility of the print, not in the immediate future.
Type Of Ink
The type of ink used will significantly affect the durability of the print over time. The recommended solution is giclee printing system that uses inkjet technology but with a far higher quality.
The giclee inks are very fine pigment inks and due to the very accurate print will result in an amazing colour gamut and spread of colours. This is often used for art productions. These art productions are normally printed on photo art paper made of 100% rag (cotton) or a combination of alpha cellulose (pulp) and rag. Because the papers are produced without any acid to achieve its whiteness thus called acid free paper.
In our ordinary day to day printers we are not using giclee inks but we can have a printer using pigment ink as appose to the dye based inks. The pigment inks in a combination with a suitable paper (bearing in mind base and coating paper recommendations) will produce the best results as far the archival properties of the paper are concerned.
Archival photo paper is normally measured by how many years the image will last and keep its original colours without change or fading. Some manufacturers promise 25 years and some 150 years. This can be put to the test and can be measured by a special machine. This machine creates light and air conditions that cut conditions that will occur over years into days and so rating the archival photo paper. Epson offers various options in A4 and A3 sizes.