Wednesday, April 27, 2016

How to avoid contamination of watercolour paper

This post is about 
  • how it's essential to avoid contamination of watercolour paper
  • how to make sure you are painting on watercolour paper free of contaminants.
I had a very interesting talk on the telephone this afternoon with Clifford Burt, the Managing Director of RK Burt who told me how contamination is the most frequent reason why watercolour paper causes problems for a watercolour painter.  It prompted me to do some more research and to write this blog post.

One of the interesting conclusions from my research is that I found very little is said in watercolour instruction books about the importance of avoiding contamination of your paper - and some said precisely nothing!

RK Burt Offices at 57-61 Union Street, London SE1 1SG
[Note: RK Burt have been paper suppliers since 1892 and are currently the largest wholesaler of fine art paper in the UK. They were responsible for introducing fine art papers by European suppliers into the UK.]

How can you contaminate watercolour paper?

There are four main ways in which watercolour paper can become contaminated.
  1. YOU can accidentally or negligently contaminate a paper. This is the MOST FREQUENT source of contamination - often due to ignorance or thoughtlessness.
  2. The RETAILER who sells you the paper can be careless in how it is stored and/or allow people with contaminated hands to touch the paper
  3. The ATMOSPHERE contains contaminants - and the paper needs to be protected from these
  4. A MANUFACTURER can accidentally contaminate a paper

How you can avoid contaminating watercolour paper

How YOU handle a paper is really important. 

"more than 90% of all complaints from artists about sizing problems with watercolour papers are due to contamination"
Clifford Burt: How to choose art papers: part three – additives | Artists & Illustrators

It is ESSENTIAL that your hands and ALL the ways in which you process your paper are free from contaminants and in particular detergent. That's because paper is made of constituents which have chemical components that can react with other substances which you introduce.

Easy ways to contaminate watercolour paper

Detergent is the main source of contamination of watercolour paper. It reacts with the size and changes the surface of the paper and how the paper reacts to paint.

If the surface of your paper has a variable consistency or performs differently in patches, the very first thing you should do is assess whether it is possible the paper has been contaminated with detergent
The paper acts like blotting paper when paint is applied
• Detergents may have contaminated the paper, which attack the size.
How to Stretch Watercolour Paper - Introduction to Watercolour Painting Part 4 | Painters Online 
Microscopic amounts of detergent are enough to cause significant problems for a watercolour paper - in patches, spots or across the whole paper - depending on the source of detergents, as these can attack the size, causing the paper to become absorbent and unusable.

How to introduce detergent onto or into your watercolour paper

  • soak your watercolour paper in the bath or kitchen sink - the homes of soap and detergent!  INSTEAD create a more controllable context for soaking paper by using a tray with sides which you can clean thoroughly (eg catering size trays or plastic germination trays come in big enough sizes)
When soaking the paper it is very important NOT to accidentally contaminate the paper with residue detergents found in areas like baths, kitchen sinks. These detergents attack the sizing causing the paper to become very absorbent and unusable.
St. Cuthberts Mill - Successful Soaking & Stretching
  • use a cup for your painting water which gets washed up with other items and dried using a tea towel which has previously dried items covered in detergent. If your water container acquires detergent it will transfer this to the water - and then to your paper. INSTEAD - have a container you only use for painting water.
  • wash up but don't rinse your hands and/or dry them on a towel which will have had contact with detergent. INSTEAD use paper towels or a towel which doesn't come into contact with detergent.
Sizing agents can be destroyed very easily by a wide range of chemicals include microscopic quantities of detergent, or even bright sunlight.
Clifford Burt: How to choose art papers: part three – additives | Artists & Illustrators
  • moisturise your hands before you start to paint. This adds artificial oils to the natural oils from your hands as contaminants on the paper.  INSTEAD clean your hands and rinse well and/or use painting gloves 

How to introduce other contaminants to your paper

  • cover your paper with photocopy or other paper which is not acid free. Other papers can introduce other chemicals on to your paper. INSTEAD use the same paper as a cover.
  • Store your paper a long time before you use it - but don't protect it from environmental contamination. INSTEAD use a flat, clean, dry and environmentally stable environment for paper storage. 

How YOU can avoid contaminating your watercolour paper

There are a number of things you can do to minimise the chances of contamination - primarily by avoiding any contact with contaminants.

Essentially reducing the scope for contact is down to the working practices you use in relation to the paper

CHECKLIST: How many of these do you do on a routine basis?

  • If you can afford to - and use lots of paper - buy unopened packs of paper
  • Store your paper flat, ideally out of the light, in a clean and uncontaminated environment
  • ALWAYS handle your paper by the edges
  • Buy a tray to soak watercolour paper in and only use it for this purpose. Make sure when it is cleaned that it is well rinsed and dried with freshly laundered tea towels (without a conditioning rinse!)
  • Use two large tubs for water - one for cleaning and one for fresh water. Make sure both are scrupulously clean and only used for painting water
  • Make sure your brushes are not the contaminant. Only use brushes which have been well rinsed after cleaning. 
  • Never protect the painting by covering your paper with anything you are not 100% certain contains nothing that can harm the paper. The best cover is always another piece of the same paper. However you also need to take care to keep cover paper away from potential contaminants otherwise it will become a vehicle for their transfer.
  • Never use a tool on the paper which is not clean and/or checked to make sure it does not contain potential contaminants.

Buying watercolour paper

The practices and performance of the retailer - and his staff - that sold you the paper is an important factor in painting on uncontaminated watercolour paper.
  • Selling paper from open packs means that the paper might have been handled by various hands - and probably none of them were completely clean
  • Selling paper from packs where the paper is only handled by the employees is preferable - but only to the extent that all those employees are "religious" about how they wash their hands before handling paper
  • Buying an unopened pack of 10 full sheets is the best way of circumventing the retailer problem.
Beware of the pack of half or quarter sheets which have been assembled by the retailer. Repackaging the paper into smaller sheets offers scope for introducing contamination. The handling required to cut the paper and stack it and insert into a pack is considerable.
  • Check how the paper has been labelled. 
  • If the label is on the inside and next to the paper it could be leaching acid out on to the paper

Archival Standard Paper

One of the things you can do to help yourself is only buy paper which meets archival standards.

However be aware that "Acid free" is not necessarily the same as archival due to the definition of the standard
Bearing in mind that the British Trade Standard definition for the paper trade of an uncoated woodfree and acid free paper can include 10% Thermo-Chemi-Mechanical Pulp and 1% lignin, it is clear that British Standards are not always what one might expect. The lignin produces acids as it degrades, thereby introducing a destructive force into the paper.

There are even some papers being sold for Artist use which include recycled fibre and are described as “acid free”. Clearly, even if a paper contains “best white waste”, it cannot be guaranteed not to contain any mechanical pulp, and the resulting lignin.

R. K. Burt - ISO 9706: How long is long life?

Protecting paper from contamination during the manufacturing process

Manufacturers of watercolour paper can protect paper from the contaminants that can be found in the atmosphere and the paper-making process. It pays dividends to investigate exactly what a manufacturer does.

Manufacturers should
  • Completely remove all the lignin - the acid in wood which can cause any paper to deteriorate
  • Use lots of water to rinse out the chemicals used to pulp and bleach wood cellulose out of any constituent of the paper
  • Use Calcium Carbonate is a buffer to help a paper withstand the negative environmental effects of the natural acidity of the atmosphere.
Interestingly even if this is done, a 100% cotton watercolour paper can still have contaminants in it which render it defective.

black specs in watercolour paper
This is an image of a sheet of 300lb Hot Press Paper produced by a European manufacturer which has very pronounced black specs embedded in the paper. Presumably these have bypassed their quality controls.

A paper such as this should ALWAYS be returned to the fine art paper retailer/wholesaler so they can investigate further. Problems cannot be identified and remedied if they are not reported.

This has been reported in my new "Fine Art Paper Feedback Group" by more than one person - and again was another reasons for this blog post.

More information about watercolour paper

There aren't enough books about watercolour paper!

If you want to find out more about watercolour paper, I very much recommend a book that I own called The Book of Fine Paper (1998) by Silvie Turner.  Not cheap but you can get second hand copies for less. (I'm looking at mine - which is still in very good condition - and realised that it has doubled in value since I first bought it!)

Artists and Illustrators Magazine produced a useful series of articles by Clifford Burt of wholesale paper suppliers RK Burt & Co about How to choose watercolour paper


  1. Thank you for this post Katherine, it really is a good balance to remind artists that the problems with watercolour paper are not always caused in the manufacturing process. I have always purchased paper in sealed packs for the reasons you describe, and am bewildered when I see how art shops sometimes display good quality paper on shelves that are open to the atmosphere and subject to extremes of temperature as well as humidity and dust.
    I use an Archival Cabinet in my studio, because this stores paper in a beautiful neutral and sealed system. In this I have stored both print making and watercolour paper from as far back as 1972, which is all in immaculate condition. A good storage system is expensive, but it will last a life time and is a very worthwhile investment.
    I wear archival gloves when moving paper from the cabinet to the easel. If I need to lean on the paper when drawing and painting, I have a piece of neutral paper placed between my hand and the paper that I am working on.

    Thanks again Katherine for bringing this to light.

  2. Many thanks for the helpful comment Coral.

    I'm greatly intrigued by the archival cabinet and am wondering where you got it.

  3. Re the Archive Cabinet - its a rather posh name for a museum quality plans chest.

    The one I have is made by the German company Otto Kind.
    I purchased it second-hand some years ago, from a conservator, and it remains in perfect condition. I'm told they are now very expensive to buy new, and can sometimes be found on eBay.

    There are quite a few companies in the UK that make this kind of cabinet.


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