View Full Version : mold on soft pastel painting

08-25-2014, 11:02 AM
Maybe baking soda will work.

Years ago I did a pastel painting that means very much to me and I recently found mold on the mat, on the back of the Strathmore charcoal paper and quite possibly on the front (not sure about that location - the couple of spots may be pastel).

Anyway, was reading on the internet that you can apply dry baking soda directly on mold to kill it or you can make a solution with water - don't want to do use the water, just a dry application.

Anyone tried this?

If it works, I am considering then applying fixative to front and back of paper, and then spray Krylon gloss UV acrylic coating to front and back to seal it and hopefully prevent any future problems as mold need oxygen to survive.

I know Krylon darkens the pastel, but I will take that over mold.

Any comments would be appreciated.

(Oh, I had this stored in a suitcase in a closet. Don't do that.)

08-25-2014, 01:09 PM
I've been looking at various articles about mildew on pastel paintings because I am starting to make my own pastels and want to use a proper mildew retardant in them. I've read suggestions such as using "a few drops" of Campho-Phenique, or some Borax (but no ratio given as to volume of water) or, more frustrating, recommending chemicals I can't find, such as beta naphthol, unless I want to purchase the product in hundred pound bags. Here is a link about using sunlight to kill mold spores. I wonder, however, if you could be sure you killed all of them before you seal your painting? If not, it seems to me that sealing it might make a perfect Petri dish for the mildew. http://en.allexperts.com/q/Painting-1461/Mildew-Print-Matting.htm

I read somewhere in another article about picture framing that mold spores are present everywhere but lie dormant until a certain temperature and level of humidity are reached. If you can keep your painting in a climate-controlled situation, perhaps the damage will not continue. If you find some good answers, please let us know! And good luck with your painting.

08-25-2014, 02:28 PM
Thanks Blayne.

Yeah, I am concerned about sealing also, but if it can keep out oxygen, which mold needs to grow, I would think it would be better than being exposed to air or sealed in a frame because there is oxygen in a frame.

I am going to take a good phtograph of the artwork, anyway, if none of this works.

Baking soda is supposed to work because it is highly alkaline and mold can't survive that.

08-25-2014, 02:29 PM
Oh, I have thought of setting it in the sun, but it so humid where I live, I might just be feeding the mold.

Barbara WC
08-25-2014, 02:39 PM
Multifaceted- what does the "mold" look like? It may not be mold- if the mat and paper are not archival, spots of deterioration may form- even if a paper is labeled "acid free", there are still chemicals in wood pulp paper that can deteriorate over time.

If it is mold, yes, sitting in the sun should kill the mold, even if it is humid- the UV light will damage the DNA of the mold and kill it. You may need a few days of exposure though.

Maybe you could post a photo of some of the damage to show us.

08-25-2014, 05:43 PM
The mold looks like brown spots. I have it in other parts of my house, so I know what it looks like. I want to move.

I guess I could try the UV rays. Are you talking leaving it outside all day? Or a few hours each day?

It is on the back of the paper and a few have started to bleed through to the front of the paper. I would be afraid to have the pastel face-up in the sun.

Also, will the brown spots go away when I've killed it? Otherwise, I won't know for sure.


08-25-2014, 05:57 PM

The link you provided is very good. I will also try to locate thymo crystals and/or thymol papers as the article says. The paper may have to be home made.

Barbara WC
08-26-2014, 12:17 AM
A good source of information is the Library of Congress. I collect old stamps and have referred to their conservation information before: here is a link to a FAQ: http://loc.gov/preservation/about/faqs/paper.html#damage

In a conservation lab, they have UV cabinets to kill mold. I don't know how long you'd have to keep something in the sun to kill mold. I'm a microbiologist and do know this would work theoretically, just not how to do this in practice.

If your piece is precious, it might be best not to try to restore the painting yourself. Pastel and the paper it is painting on, are fragile, and you may do more damage than good if you start using chemicals.

I am almost sure that baking soda won't cure your mold problem- I believe what you might have read is that baking soda (which is alkaline) might help with the acidity in wood pulp. However, I don't think dry baking soda would do a thing for your paper- it won't kill the mold, and since it is dry, it won't do much to help with any acidity in the paper.

Personally, what I would do is leave the painting alone. Remove any matting and tape, and then place the painting between two pieces of archival buffered paper (this is what I do for stamps). Then store it maybe between two pieces of archival backing board, and somewhere with some air circulation (not under a bed, more like in a living room).

Another option is to mount it on a piece of archival buffered paper, matt it with an archival matboard, and frame it. Hang in the driest room in the house.

I get my archival mounting supplies for stamps at: http://www.lightimpressionsdirect.com/

Edited to add: Just so folks know, just because something is labeled "acid free", does not mean it is archival and meant to last for decades. An acid free paper often still contains wood pulp, and unless it is buffered, can deteriorate over time.

Barbara WC
08-26-2014, 01:22 AM
Forgot to add: no, the brown spots won't go away even if you kill all the mold on the paper. You may be able to remove some of the mold, but the brown spots are caused by the mold degrading the paper itself. The paper can be restored by a special bleaching method- but my recommendation is to not attempt it yourself.

Have you thought about contacting a conservator? It might be pricey, I have no idea how much, but if the painting is that precious to you, it might be worth getting it restored before it degrades further.

08-26-2014, 05:03 AM
The brown spots are actually the mold itself. Even if you kill it, the millions of microscopic cells that make up its structure will indeed remain on the paper. They will just be dead, and thus the spots will not grow any bigger. You can get rid of some of it by brushing it off, but since it also grows under the surface of the paper, the only way to remove the spots is to bleach it. And there again the cellular structure will still remain; it will just be invisible. I mention this because many species of mold have spores that can lie dormant in very inhospitable conditions for a very long time only to grow again when things become more appealing. So whatever you do to this painting, you need to always watch it carefully, because there will always be a danger that the mold will grow back.

I know a bit about mold, since my first college degree was in microbiology, which is at least 50 % about mold, and other things that look like mold! I know of many ways you could kill this pest, but the problem is, most of them would destroy the painting. At the very least, most chemical applications would be likely to react with the paper or the pigments in the painting, speeding deterioration. Borax, for instance, is boric acid, which will degrade both pigments and paper over time. We use acid-free papers for this very reason.

Baking soda is a fairly safe solution, and depending on the species of mold it should help slow down or stop the growth. Multifaceted is right--mold does not like to grow under extremely alkaline conditions. However, the bad news is that it will not kill the mold, no matter how heavily it is applied. It is fungistatic, not fungicidal. The mold will not grow as long as the alkaline environment remains, but as soon as it wears off (which may take years or decades, I'm not sure), it will start germinating again. But I think it may be the best bet you have.

What I would do is combine the baking soda treatment with an extreme dehydration. Mold (or anything, for that matter) cannot grow in the absence of water. Getting your paper perfectly dry is as important or more so than anything you could spray on it. I recommend taking the painting out of the frame, taping some glassine to the front to protect it, and then sprinkling the baking soda on the back. I may leave it that way overnight, to give the baking soda a chance to sink into the semi-moist paper (it must be moist, or the mold would not be growing there). Then, I would dry it very gently in a warm place, such as by a space heater, or on a rack on top of the stove with the oven on a low heat, until it is bone dry. Do this for a few days if you have to. Finally, I would put it in a tupperware container with a bunch of those silica beads that come in packages in vitamin bottles and leave it there for a few weeks. After that, it should be safe to frame. I would not spray Krylon on it. Some Sennelier Latour will work just as well and not destroy the colors. You might want to spray it on before you do all this excessive drying.

On a side note, it is strange to me that the mold started in the first place. It usually only germinates in acidic environments. Did you use acid-free paper?

08-26-2014, 05:16 AM
Impressive knowledge shared here, thank you!

I had two suitcases stored in the garage, and they molded on the inside... while pastel paintings in frames/glass in the same garage showed no sign of problems. Possibly because they were on shelves, like books, loosely stacked so air could circulate and carry off moisture.

If you try the baking soda, be aware of the fact that the soda attracts pastel particles and will carry them off. You would have to repair the painting.

Would it be possible for you to re-paint the painting, instead of trying to save it?

08-26-2014, 10:20 AM
Well, this is a lot of good info. Thanks for all the suggestions.

The painting was not framed, just matted, and all materials including the Strathmore paper is acid-free. I found some mold in my closet which found its way to my painting inside the suitcase.

I would have had it framed a long time ago, but I have been dealing with some health issues that left me in bad shape for quite a while. That is why the piece had been abandoned for so long.

The paper does not seem moist at all, but maybe there is some humidity even with air conditioning. But in the winter we use a wood stove which really dries the house very well.

I am also wondering about using a fairly light misting of lysol on the back where most of the mold is. Don't know if this would harm the paper over time. If so, how much time?

I was reading a website by a conservator in New Orleans stating that with paper it was best to lightly spray with lysol until they could deal with it. And they stated they would put it into a fungicide chamber.

So I'm thinking that a light misting of lysol might be safe and after it is totally dry, store it in a tuberware-type container and maybe that would be like a fungicide chamber, since some of the lysol would still be present?

Also, the idea of laying it on top of the stove might work. Incidently, I had silica beads inside the suitcase thinking that would protect it until I felt better. Crazy mold. It has a mind of its own.

I would consider repainting, but the dust causes me problems now.

I now work in oil pastel, which I also love.

08-26-2014, 11:33 AM
I've learned a lot from all the posts. I'm glad you started this thread! And I'm sorry to hear you can no longer work with soft pastels because of the dust.

08-26-2014, 12:20 PM
Thanks Blayne. I'm learning a lot too.

Yeah, soft pastels are wonderful. I miss going across the paper with the soft pastel stick and working in a creative fever, but I really love oil pastels, too.

They are more like oil painting and a joy to work with. But, I am still learning.

Here is link about using lysol: http://www.art-restoration.com/damage.htm

I am experimenting with spraying a light mist of lysol on some scraps of the strathmore paper to see if it buckles, because it is a lighter weight than Mi-Teintes.

But it is decent paper. I was using it for both soft and oil pastel 25 years ago, and it is still in good shape. The colors have not faded and, with the oil pastel, I used a very hard Grumbacher brand (no longer made) and disolved it with turpenoid, and the paper is still in good shape. The oil in oil pastel is supposed to be inert and therefore safe on good quality paper. Although, the jury is still out on that one.

So, if turpenoid didn't hurt the paper, maybe lysol spray won't either?

Now, I am using the very soft oil pastels and am having to learn all over again, but they are beautiful.

But after this experience, I am wondering about using paper at all.

Barbara WC
08-26-2014, 02:52 PM
I just wanted to reiterate, just because a paper is labeled "acid-free", it does not mean it will last indefinately. For the longest life (centuries), choose an archival paper. Not just acid-free. Most acid-free papers are made from wood pulp from which the acid has been removed, but environmental conditions can cause an acidic environment to occur and the wood pulp will start to deteriorate over time.

Archival papers can either be: 100% cotton rag, or buffered alpha-cellulose. The buffered papers have calcium carbonate in it at a ph of 8.0 or 9.0. This is absolutely necessary for alpha-cellulose paper, not as necessary for cotton rag papers.

HOWEVER, even when using regular acid-free paper, there are things that can be done to keep the painting for longer than your lifetime:

First, mount on an archival board and use an archival matt. Whether you choose cotton rag or alpha-celluose backing boards and matts, be sure they are buffered, at about a pH 8.0 or 9.0- this is important to stabilize a painting done on a questionable paper- if there is any acid that migrates from the environment into the wood pulped paper, the buffered backing board will neutralize the acid and keep harm away from the painting. Then frame the piece and keep it in the least humid place in the house. Or, if you store it somewhere, best to place in an archival, buffered matt between two archival backing boards, and place upright and keep in a portfolio where it will get airflow- not under a bed, for instance, but in an art room. As importantly, use archival tape to mount. I like: http://www.lineco.com/cart.php?m=product_list&c=581&primary=1&parentId=&navTree[]=1257&navTree[]=2085&navTree[]=581

Those of us who paint on coated, sanded surfaces are mostly painting on archival surfaces because the paper has a sealing layer. However, another concern is the paper the coating is on- for example, Wallis museum grade uses 100% cotton rag (which is archival) versus the professional grade (which is on acid-free paper). If you want your paintings to last for a very long while, paint on a paper that says it is "archival" (I use PastelMat which claims it is archival, but I can't find much information on how the paper is made).

But even works on Canson Mi-tientes can last a very, very long time, as long as the painting is properly stored- which like I mentioned above, it should be mounted on archival board and have an archival matt, and either framed or stored somewhere upright in a portfolio, ideally in an air conditioned and heated room with some air circulation.

Archival matting and storage is costly, and not necessary for every painting, but I usually use archival framing methods if I am painting a special painting and giving it as a gift, or if I produce a favorite painting and want to make sure it lasts. I have taken a couple of older paintings on Canson Mi-tientes, with no visible damage yet, and put them in archival matts and on backing boards to ensure they last longer.

There is much more information on the web, if you search archival storage. I collect old stamps and learned a lot about how to store these precious items for the long term, and have carried it over to my artwork.

08-26-2014, 04:37 PM
Thanks Barbara.

Well, I have sprayed the back of the artwork with lysol spray and have let it dry.

While looking at the other artwork stored with this (put on my reading glasses), I found some spots of them as well, so took the lysol (light mist) to them as well. I also left them in the sun a while. We shall see with time.

I appreciate everyones help and feedback.

I've seen some beautiful work on this pastel forum.

08-26-2014, 05:20 PM
Thanks Barbara.

Well, I have sprayed the back of the artwork with lysol spray and have let it dry.

While looking at the other artwork stored with this (put on my reading glasses), I found some spots of them as well, so took the lysol (light mist) to them as well. I also left them in the sun a while. We shall see with time.

I appreciate everyones help and feedback.

I've seen some beautiful work on this pastel forum.
There's a lot of useful info in this thread...thank you for asking the question! I would like to copy this thread to the Soft Pastel Archives - for threads of importance , if I may, so others will be able to find it easily?

08-26-2014, 06:17 PM

Yes, there is lots of good info here and you may copy to Soft Pastel Archives.

I hope all of this can help someone else.

08-26-2014, 06:25 PM
Thank You....I will copy it now!:wave:

08-26-2014, 10:41 PM
hey Alan Flattmann says in his book he steams them with clove oil or something. Being from N.O. he probably knows about it well. Look into it! Good luck... it is bound to be safer than lysol, no?

08-27-2014, 06:02 PM
Now that's an interesting idea.

Hopefully it will get posted to the archives as well for anyone else with this problem.


08-28-2014, 03:13 AM
Fantastically informative and interesting thread.

In a conservation lab, they have UV cabinets to kill mold. I don't know how long you'd have to keep something in the sun to kill mold. I'm a microbiologist and do know this would work theoretically, just not how to do this in practice.

Here's a probably silly thought: A few hours at a tanning salon?

And if molds need loads of oxygen to grow, an ozone generator in a confined space together with the mold might possibly help. (I know, I know, effective ozone generators for home use aren't exactly common, and the ones for professional use can be quite dangerous.)