Checking artwork for mold contamination (C) D Friedman Ulrik Runeberg Testing for Mold Contamination in or on Artworks using Light Microscopy & PLM

  • ARTWORK MOLD CONTAMINATION - CONTENTS: Mold contamination on works of art, paintings, drawings, photographs, other materials. Distinguishing among mold contaminants, other particulate contaminants and other stain sources on or within paintings and other works of art. Extractive bleeding in art works painted on hardboard products such as Masonite® or Upson Board.
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Mold contamination on or paintings or other artworks:

This article describes using transmitted & reflected light microscopy and polarized light microscopy to test for and report on the appearance of mold contamination on works of art (typically in the museum or in-building environment) and a forensic microscopy approach to detecting mold contamination on artworks in order to assist art conservators in both removing mold contamination and in preventing it on these materials.

We include a discussion of distinguishing among mold and other painting contaminants, stains, including extractive bleeding stains, their causes and prevention. Other sources of biodeterioration of works of art such as cave paintings, and algal growth on outdoor materials are discussed elsewhere.

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Mold on Art Works, paintings, painting substrates, other artworks or cultural artifacts

Photo of mold on  refrigerator/freezer surfaces(C) Daniel Friedman Photo of mold on  refrigerator/freezer surfaces(C) Daniel Friedman

We have assisted several museums & curators with mold diagnosis, cure, & prevention on works of art.

The control of indoor humidity where works of art are displayed or stored indoors is naturally the principal step taken to protect these items from mold damage.

Additional steps to protect artworks depends on the materials used and the value of the items.

No valuable artwork should ever be sprayed or coated with a fungicidal sealant without consulting with an expert art conservator, and where an artwork has become mold damaged, amateur cleaning can damage it further - consult with an expert art conservator for advice.

Inoue has tested a varnish coating supplemented with fungicide to attempt to control mold growth on painting surfaces [16] and Krake et als. have evaluated microbiological contamination of artworks studying both the face and the back side of canvases in a museum. [17]

In some cases it may be possible to frame, enclose, or treat the back surface of some paintings without damaging the work itself nor impinging on its artistic or monetary value. Take care to distinguish between mold growth and other moisture-damage to artworks.

Our photographs above illustrate mold growth on the paper backing of a framed work of art - mold that affects art and artifacts may be hidden on unobserved surfaces but may still be damaging the work.

Checking artwork for mold contamination (C) D Friedman Ulrik Runeberg

Our page top photograph illustrates a finding of mold growth (Cladosporium sp. and Penicillium sp.) on the surface of an oil painting. At left, other stains that appeared to be mold needed just a little further examination to distinguish between mold growth and hardboard wood fibers.

In performing analysis for oil paintings displayed in a museum in San Juan, Puerto Rico, working with art conservator Ulrik Runeberg ("Staining and Microbiological Infestation of Acrylic Paintings on Hardboard" [3]) we discovered that "brown spots" that looked like mold contamination were in some cases brown oils or extractive-bleeding from Masonite-type hardboard on which the paintings had been executed.

(Pair of photographs shown just below.)

Had the artist first sealed the hardboard surface with a suitable sealant, perhaps a lacquer primer, that staining would have been reduced or prevented entirely.

Mold on artwork study (C) Daniel Friedman Mold on artwork study (C) Daniel Friedman Examining oil painting base fibers for mold contamination (C) Daniel Friedman Eric Runeberg

Our photo (left) shows a higher magnification examination of fibers from the art-work above, as we checked for mold spores or a different cause for discoloration found on the painting obverse side.

Other artworks we have examined suffered severe mold damage, including a wide range of media such as paper-based prints and lithographs or etchings and oil paintings on canvas.

While indeed we often can find mold contamination growing on the surfaces of paintings and other art works, we may also find mold contamination within pigments - possibly from the time of creation of the work - changing the conservator's cleaning and maintenance strategy.

We also often find surface or in-media contaminants that were not mold, though they have been mistaken for it.

These other contaminants include insect fragments, soot particles, road dirt and debris particles, fabric fibers, and even ultra-fine spray paint droplets that, unless examined properly, are mistaken for different contaminants, thus risking misleading the art conservator in her planning for art or artifact restoration or maintenance.

Artwork contaminants - paint droplet (C) D Friedman U Runeberg Artwork contaminants - paint droplet (C) D Friedman U Runeberg

Our photos above illustrate an example of potential confusion. By transmitted light (photo above left) the round particle may look like Nigrospora sp. or another fungal spore. But by reflected oblique top lighting it becomes immediately obvious that we are looking at a fine spray paint droplet, in this case of white-pigmented paint.

When appropriate we provide pro bono or fee-paid forensic investigation services to museums and art conservators.

Humidity & Mold on Art Works

The control of indoor humidity where works of art are displayed or stored indoors is naturally the principal step taken to protect these items from mold damage.

Watch out: While some experts recommend that paintings and murals must be stored at a relative humidity of 60-70%,[38] our opinion is that those humidity levels are considerably too high to be safe because

  1. Many fungi are quite happy at 60-70% RH
  2. Our field measurements show that there is often a significant difference between the humidity at the point of measurement in a building and the humidity on or close to building exterior walls (where the RH may be much higher). Details are


Continue reading at BOOK MOLD, CLEANING or select a topic from the More Reading links or topic ARTICLE INDEX shown below.

Or see

ART CONSERVATION - Cultural Heritage and Aerobiology describes a text that offers some help in controlling mold and other sources of damage to paintings as well as other cultural artifacts.


BLACK LIGHT & UV LIGHT USES including finding mold, animal urine, other biological materials



FOXING STAINS on books & papers - cause and cure

MILDEW REMOVAL & PREVENTION - mildew is often a mis-applied term since it is a form of mold that grows only on living plants

MOLD RESISTANT CONSTRUCTION discusses methods to reduce the risk of mold growth not only on building surfaces but on and in the contents found in buildings, including works of artifacts and works of art such as paintings.

Suggested citation for this web page

ARTWORK MOLD CONTAMINATION at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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