Acidity in UART paper – A message from our CEO

This whitepaper was written to specifically address the concerns of many pastel and colored pencils artists regarding the archival quality of UART paper. The concerns stem from some artists who used a pH testing pen to determine whether our paper was acidic or not. Since the pH pen indicated the presence of acids, artists became worried that an acidic pH level in the paper means that the paper will deteriorate over time and that their workpiece will be destroyed in the process.

At UART, we take the concerns of every artist very seriously and wanted to respond to those concerns with the most scientifically accurate information possible. We perfectly understand that artists worry about the archival quality of the substrate they use and want their paintings or drawings to last as long as possible.

Unlike other sanded pastel papers available on the market today, UART paper can be considered as a true sanded paper. It is constructed with a paper backing that receives multiple layers of resins, grain and glue which confer the paper its unique properties. Most sanded paper on the market are made with a cotton base backing and follow a manufacturing process much different than ours. One of the major reasons why you can use all types of wet media on UART paper without affecting or damaging the surface is the added layers of specific resins and glue that provide a very sturdy and durable material. But before we continue, we would like to offer you a bit of paper history to give you some perspective.

Paper, as we know it today, was first made in China by Ts’ai Lun, a Chinese court official, in the 2nd century AD. In all likelihood, Ts’ai mixed mulberry bark, hemp and rags with water, mashed it into pulp, pressed out the liquid, and hung the thin mat to dry in the sun. Over time, technology helped refine the production of paper, but the base always consisted of cloth and that has been the case up until the mid-1800’s. As the demand for paper started to grow exponentially in the 19th century, the mills moved to wood pulp because wood was less expensive and more abundant than cloth. Many chemical additives, such as aluminum rosin were progressively added to the wood pulp to reinforce the structural bonds in the paper and minimize bleeding of inks. While these additives gave initial strength, they were also a source of great acidification. They dramatically lowered the natural pH of paper to a range of 3.0-4.0, which inevitably resulted in diminishing the longevity of paper. This production process remained the same until the 1980’s when paper manufacturers began adding alkaline buffers to wood pulp papers to achieve a much more stable pH range of 6.5 – 7.0. This new chemical process still remains standard practice to this day.

Trying to determine the quality and durability of any paper product using a low technology device, such as a pH pen for instance, is problematic and can be very misleading to the end user. A pH pen will only tell you if a substrate is acidic or alkaline. It will not provide you with a specific pH level. Therefore, the paper tested could have a pH of 6.7 and still register acidic with the pen. A paper with a pH level of 6.7 or slightly lower will not, at any point in time, deteriorate at a faster rate than a paper with a “neutral” pH of 7.0. The vast majority of the paper that is manufactured today, except for low quality substrates such as newspaper, are made with chemicals that will not affect the long term durability of the paper. There would only be reason for great concern if the actual pH of the paper is lower than 4. UART paper backing registers a pH level of about 6.5.

It is imperative for us to provide our customers with the most accurate information possible, so that you can make an informed opinion when purchasing our paper. We understand that many artists have the best of intentions when they test our paper and are striving to inform the consumer the best they can. We, as manufacturers, also need to make sure that the information that is shared to the world is as accurate as possible. We always stand 100% behind our products and guarantee that our sanded paper, under normal and stable conditions, will not deteriorate over time. Let us also show you a test performed by one of our artists who lives in Israel. She volunteered to put UART paper to the test and exposed our paper to the harsh Mediterranean sun for over 5 months. Although the testing process remains relatively “unscientific”, you will see that not only did our paper remain completely undamaged by the sun, it also did not fade and stayed 100% lightfast. You can read about the results HERE.

We hope that the information we provided you here was helpful and cleared any doubts you had about UART paper. We remain available for any questions you may have about our paper and we hope that you will continue choosing UART as your preferred surface for your paintings and drawings.

Happy painting!

Bruce Fuchs
UART Premium Sanded Paper