Photo paper

Unlike other types of paper, photo paper is a special type of paper. It is usually thicker and the colours have more luminosity, brilliance and vibrancy. You also need a high-quality printer that can print on this type of paper and achieve the same colour intensity.

At print24 you can find out exactly what properties photo paper has, what types are available, what types of printers are suitable and everything else you need to know about this type of paper!

What is photo paper - the basics

Photo paper is an image printing paper that has a special coating. This coating or the binder/coating consists of kaolin, chalk, casein or even plastic dispersion. The special treatment of the photo paper makes it more supple, stable and smooth than normal paper. It also means that the ink is not immediately absorbed, resulting in a high print quality. This means that the printer's ink does not run and the result is razor-sharp images with rich colours.

In general, four types of paper can be distinguished: Porous, cast coated, microporous and swellable, although only two of these are suitable for photo printing. Very often, photos for self-printing are printed on swellable or microporous paper coatings. The ink is adsorbed, i.e. it is deposited between two layers on the surface instead of penetrating the inside (absorption). Plain paper such as offset paper usually has no barrier between the coating and the backing paper, so the ink is absorbed directly by the base layer (undercoat). If too much ink gets onto the layer, the paper starts to curl (cockling). It can also happen that it runs (bleeding). This is prevented with photo paper, which has waterproof barriers on both sides, i.e. PE films (polyethylene layers) that keep the backing paper dry. The PE films also give the photo paper additional support.

There are differences between microporous and swellable types of paper in the way they absorb ink. Swellable coatings can be made of gelatine but also polymers, they are water-soluble and water-sensitive. The coating absorbs the ink liquid and thus swells. The liquid then dries, but only the water evaporates and the ink substances remain. In the process, the volume of the paper surface decreases again. The swelling time takes longer than with microporous photo papers. It is important to know that as long as the surface of the photo paper is still swollen, it is still very sensitive and can therefore easily get scratches or pressure marks. Also, swellable photo paper is relatively incompatible with pigment inks. On the other hand, it is suitable for dye inks because the dye is dissolved in them. The advantage of swellable paper is that the dyes are enclosed in the polymer matrix. This means that oxidative gases, such as ozone, have hardly any surface to attack.

Photographic paper with microporous coatings is different. Here, a type of silicic acid coating (silica) is additionally applied to the PE film. This causes the ink to be drawn deep into the layer by capillary action. It is deposited on the silica components, which are shaped like glass beads. Thus, the surface of the photo paper feels dry immediately and is rather insensitive to touch. Nevertheless, a certain drying time should be observed so that the water can evaporate well. If the photo paper is placed behind glass immediately after printing, it can be observed that the colours run into each other. This is due to the fact that besides the ink, gases also penetrate the photo paper, which means that the ink molecules are less protected. Due to the clarity of the coating, a very high colour brilliance results.

In summary, swellable or microporous paper is suitable for photo printing. The base provides sufficient stability, and temperature and air quality have no influence on the paper's behaviour under normal circumstances. Since swellable photo paper can sometimes no longer absorb ink at humidity levels below 20 per cent, is not compatible with every type of ink and requires a longer drying time, microporous paper is often preferred for photo printing.

The different coatings of photo paper

Basically, photo paper is available in matt, satin and glossy.

The surface of matt photo paper consists of a disordered relief, it is accordingly uneven. As a result, the light is reflected over a larger angular range and is not concentrated in one spot. This creates the subjective perception that matt photo paper has less luminosity. However, if glossy and matt photo paper are placed next to each other in the same lighting conditions, they can hardly be distinguished from each other. It is only when the light source moves away that the lighting conditions lead to an even reduction in colour saturation and contrast. On the other hand, matt photo papers look very good from different viewing directions, while glossy papers already show strong reflections.

Glossy photo paper has a smooth surface and sharp reflections. This makes the photographs appear more colourful and detailed. Depending on the type of paper, the light is reflected more strongly. This is why glossy papers also exist. The disadvantage of these photo papers is that the high reflection can lead to fading of the photos, which also makes them less suitable for exhibitions. In addition, fingerprints can remain permanently on glossy photo paper.

Semi-gloss paper is similar to glossy photo paper in its properties. It reproduces colour excellently, as well as colour subtleties. Unlike glossy photo paper, however, there are hardly any reflections on the surface, making it suitable for exhibitions.

For lower-quality, pixel-heavy images, the use of matt and side-matt photo paper is recommended, as blurring is less noticeable.

In addition to these common types, there are also some less common types of paper. Metallic photo paper, for example, is a special paper that makes colours particularly vivid. In the same way, the photos have an extremely high gloss. All this makes for very good effects, which is precisely why attention should be paid to the choice of motif. Silkscreen is another type of paper and is preferably used for portraits, which is why it is sometimes called "portrait paper". It has a very noble and silky sheen as well as a firm structure. The structure is the main reason why photographers prefer to use this photo paper for portraits.

The weight of photo paper

In addition to the different coatings, photo paper differs from plain paper mainly in its thickness, or weight, or strength. It is thicker, similar to cardboard paper. The grammage (weight per square metre) for swellable paper is approximately between 120 and 300 gsm, for microporous photo paper it is 170 to 300 gsm. In comparison, copy paper has a grammage of about 80 gsm. Depending on the grammage you choose, a normal photo printer, inkjet or laser printer can still print on the photo paper. However, the heavier the photo paper is, the heavier the print will be, sanding marks may occur and some printers will not feed the paper at all. It is therefore recommended to check the maximum possible grammage of the sheet for your printer before buying photo paper and to use thinner photo paper if necessary.

For printers, there is the classic A4 photo paper, but there are also smaller formats. There is also special photo paper that can be printed on both sides. This means that not only one but both surfaces are coated. This form of printing is also called duplex printing.

The right photo paper for successful use

As has been shown in the meantime, no one photo paper is suitable for all applications. Several different papers are manufactured for a specific purpose. Therefore, it is advisable to think in advance about what kind of print you want to make and what the photo will be used for.

Probably the oldest photographic paper is called baryta paper and was developed by Martinez-Sanchez and J. Laurant in Madrid in 1866 as a base for light-sensitive emulsions. It is ideal for black-and-white printing and consists of high-quality base paper, which in turn consists of cellulose with binders and fillers. To produce white photo paper, an optical brightener is added to the cellulose mixture, while paper tones such as chamois or ivory are given additional dyes. Baryta paper is relatively expensive and very difficult to process and should therefore only be used for black-and-white prints.

The next type is PE paper, a photographic paper that is surrounded on both sides by a plastic coating of polyethene. The surface itself consists of a polymer layer that prevents the colours from smudging immediately after printing and keeps them in place. Thus, photographs on PE paper have a high quality and are colourfast. The only disadvantage is that printing takes some time.

Nanoceramic photo paper also has a plastic coating on both sides. The difference is that it has a nanoceramic layer instead of a polymer layer. This has very porous properties and therefore allows the ink to pass directly through and dry. The photo print has an outstanding quality, furthermore, the surface is completely waterproof, which is a big advantage. A disadvantage, however, is that the surface is at the same time impermeable to air, so the colours fade and the quality can be affected if the photograph is used often. The nano-ceramic photo paper is therefore suitable for mounting in a picture frame.

Inkjet paper is another type of paper that has only one layer and can be used for almost all inks and printing techniques. However, it achieves a lower image quality than other types of paper because it has a rather matt surface. On the other hand, it is advantageous that inkjet paper dries quickly.

Durability of photo paper

The durability of photo paper depends on the type of paper, the ink used, appropriate storage, prevailing temperatures, gases and humidity. It is shortened if, for example, the photograph is exposed to constant UV radiation, is stored without protection in damp rooms or comes into contact with harmful gases. If, on the other hand, it is stored and/or framed properly, it can last up to 200 years.

The type of paper as a durability factor for photo prints

If paper is used that has some optical brighteners, the photo print may yellow more quickly. In addition, brighteners decompose over time, so the reflectivity decreases and the photo print loses its ability to reflect UV light. The photo paper takes on what appears to be a yellowish colour, which is just its natural colour without the added brighteners. To slow down the decay process and the associated discolouration, protective sprays can be used or the photograph can be framed in UV-shielding glass. There are also whitening agents that decompose less quickly. Nevertheless, the process cannot be stopped completely, as the lignin is the reason for the discolouration. Lignin-free photo paper is therefore particularly suitable for archival purposes, such as photo paper made from alpha cellulose or cotton linters. Durability is also increased if the paper is acid-free (pH-neutral), in which case the use of neutral glue becomes necessary. However, since even pH-neutral photo paper can accumulate acid over time, the papers can be buffered with one to two per cent calcium carbonate and thus shifted into the alkaline range. However, if the photo paper is basically acid-free and also free of possible acid-producing substances, acid accumulation is unlikely.

Ink as an influencing factor for the durability of photo paper

In addition to the type of paper, the ink used is also decisive for the durability of photo prints. Pigment inks differ from dye inks in that they are less sensitive because they have larger dye particles. The tiny dye particles of dye inks can withstand UV rays or gases for less time than those of pigment inks. However, due to technical progress, huge improvements have been made by encapsulating pigment particles of pigment inks with a resin shell. This creates a barrier that prevents the particles from sticking together. In addition, negative electrostatic charges occur inside the resin layer, which increases the repulsive forces between the particles. This results in free-flowing inks with lower viscosity, which no longer clog printhead glands. Alternatively, there are pigments enclosed in resin that are pulled apart by a polymer used to prevent them from sticking together. As a result, photo prints become more lightfast, waterproof and smudge-proof.

In principle, the durability of photo prints is improved if they are first given sufficient time to air out. Only then should they be framed behind film or glass. Up to 24 hours is recommended here. It is also important to keep them as far away as possible from UV radiation, harmful gases such as ozone, high temperatures and high humidity. Accordingly, it is best to store the photograph behind (UV-repellent) glass that is not exposed to direct sunlight. Likewise, photographic paper should not be stored in attics with sometimes high temperatures or in damp cellars. The kitchen, bathroom or the immediate vicinity of radiators are also not recommended. If you want to store your photo paper in plastic film, it should be of the highest purity and, if possible, not contain any acid. Plastic sleeves are recommended here, as are those made of polyester, polypropylene or polyethene.

Various motifs printed on photo paper with print24

At print24 you have the opportunity to have versatile photo motifs printed on a wide variety of printing materials. Whether you are looking for photo stickers, photo books, photo chairs, photo doorplates, smartphone cases or even photo mugs - there are almost no limits to your wishes. If you have any questions about our services or about photo paper, please feel free to contact us at any time, we are at your disposal!