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Old 20-05-11, 07:11 PM
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EllenT EllenT is offline
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Default Using MDF anyway?

Hi All,
A few months ago I ordered about six panels from a carpenter here in Belgium. Three required some special work. I thought I had specified plywood but when I went to pick them up, discovered that the panels he had prepared were MDF - which I have never used before. Of course I protested, but since it was a miscommunication - and in another language - I decided to see if I could make it work, not knowing about the bad rap I am now encountering about MDF.

If I understand the problems they are the following:
  • unknown oils may have been used in the production of the panels which may cause the gesso to separate from the support over time.
  • those same unknown oils may leach into the gesso and thus the painting, also over time
  • the fibrous nature of the panels will naturally absorb moisture at the edges causing swelling over time
  • any more I'm not aware of?
Since I am now stuck with boards, I'd like to go ahead and use them but hope to take precautions as best as I can. Thus, if I sand the panels well and glue a piece of linen to them as though they were plywood can I (hope to) escape the first two potential problems? Does anyone have experience with doing this?

Any tips on sealing the edges well? Would acrylic gesso, since it is less hydroscopic, be a possible candidate?
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Old 21-05-11, 08:51 PM
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DLH DLH is offline
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I have a theory, (I hope one day to test.) that traditional gesso is the best protection from moisture uptake in a panel. While not being watertight itself it has a tremendous capacity for storing water in moist weather and then giving it back to the atmosphere on dry days, thus preventing moisture from reaching the panel. Think about it, when we make glue we can easily add 20 parts (by volume) of water to 1 part glue and it will still be a gel at room temperature. Dry gesso consists of stone particles held together by tiny filaments of glue. There remains more empty space between the stone particles than is taken up by the glue. The glue can swell a great deal before there is any effect on on stone or panel. This is also the principle behind those magic diapers that can hold a liter of water. They have a gel core. Traditional impervious coatings cannot totally seal, so the panel will swell thus cracking the coating and allowing even more moisture in.

I apply a 1.5mm or thicker coating of gesso to the edges of my panels. (as well as the back) the sides and back then over coat with white paint.

When I started painting I thought a lot about these issues as well as other insults a painting could endure. I was concerned the panel edges were particularly vulnerable. It is easy to knock and edge do to mishandling. my solution (besides gessoed edges) is to paint a "mat" on my paintings. This has now become part of the painting design and ranges from 1cm to as much as 10 depending. This buffer zone is easy to repair should the edge be damaged. The deliberate mat and integrated edge adds a feeling of gravitas. I hang my paintings with hidden 1cm spacers sans frames.

Last edited by DLH; 21-05-11 at 08:54 PM.
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  #3  
Old 22-05-11, 01:00 PM
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EllenT EllenT is offline
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Default using MDF anyway...

Hi DLH,
Thanks for the response. Yes, the RS component in gesso contains "magical" organic absorptive properties that can indeed work wonders in a variety of circumstances. And yes, I, too usually coat both sides and the edges of my plywood panel, so I would plan to do the same with the MDF panel(s).

It seems to me that there are two issues here: one is the bond between the gesso and the support, the second is the bond between the gesso and the paint. If I want to aspire to archival quality in my paintings, then both bonds need to be very good. If I use MDF, my concern is the fragility of the initial bond between the support and the (true) gesso. I'm not sure the resilient qualities of the RS component could make
up for the lack of absorbency in an MDF panel and thus my question.

I like your idea of painting in a 10 cm frame all the way around in order to keep the friable edges well outside the significant inner image.
Cheers,
ET
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  #4  
Old 26-05-11, 02:22 AM
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Koo Schadler Koo Schadler is offline
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Hello Ellen,

A few thoughts on your question. First, my understanding is that the oils used in tempering hardboards are drying oils - meaning that they cure, or polymerize, over time and are then irreversible (can't go back to being gooey). This makes sense, as I don't think a manufacturer would want non-drying oils - they might not only leach into a painting but, more important to the manufacturer, might also pose a problem for a builder, their primary customer. So if this presumption is correct, that the oils in tempered boards are drying oils and cure, I don't think there is any worry of them traveling into your gesso or painting.

However tempering oils, even drying ones, might interfere with the adhesion of gesso to the surface. Additionally, some hardboards and MDF are tempered with wax, which could also affect adhesion. So I do think there could be a problem in that regard.

How long before a problem, such as separation between gesso and panel, arises? Maybe in a few years, maybe in fifty, maybe never...these archival questions can be hard to answer because there are so many variables (how much and what type of tempering is in the panel, how well is the surface prepared, how strong and well made is your gesso, what conditions does the painting live under, etc). The other relevant issue is, how long do you want your painting to last? Some people care about their work being archival, others don't.

My guess - and truly it is a complete guess - is that if you prepare your support well (more on that below), make high quality gesso, and store the resulting painting under favorable conditions, it would probably last for a pretty long time... a lifetime or two, if all the variables were favorable?? Totally a guess. It is only to say that tempered hardboard or MDF are not necessarily deal breakers if one is diligent in other regards (and I say that as a devoted fan of the UNtempered variety).

To prepare a hardboard or MDF support well, here are some suggestions: 1. Lightly sand the panel to lift off any stray nubbins of anything that may be stuck to it, as well as to open up the surface (so use sandpaper with a bit of tooth, such as 180 grit). 2. Next rub it down with denatured alcohol to remove greasy fingerprints. 3. For your first layer, rub in a coat of rabbit skin glue and let that dry overnight, before applying the gesso layers. 4. Make a great gesso! (i.e. use the best glue you can find, don't overheat it, etc).

There is one more relevant topic in regards to MDF boards which is that sometimes, I believe, they contain formaldehyde. I don't think there is any question that overexposure to formaldehyde is bad for one's health, but I'm not sure how long a panel will out gas. Indefinitely? Or just for a few months after being made? I don't know..out gassing may be a mute point by the time it enters your studio, but maybe not. And will out gassing, if it actually does continue to occur, affect your painting (as well as you)? I don't know that either. Perhaps one of the chemically savvy posters out there can tell us more.

Eric Thomson wrote an informative article on hardboard that addresses some of these issues. Its several years old by now but still relevant. www.truegesso.com posts it on their website, at:

http://www.truegesso.com/~truegessol...%2011-6-08.pdf

Good luck.

Koo

PS - Love your gesso/moisture theory DLH. I buy it. I'm sure you also know that another one of the magical properties of gesso is that its alkaline nature beautifully counters the acidity of wood. What a substance....

Last edited by Koo Schadler; 26-05-11 at 01:49 PM.
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  #5  
Old 26-05-11, 02:28 PM
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EllenT EllenT is offline
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Default MDF questions

Hi Koo,

Thanks very much for your informative answer. It all makes sense. Common sense tells me that European manufacturers might not be using formaldehyde, but I certainly don't know.

I have already begun by sanding my panels - actually with a pretty coarse grade - and have applied a thin cotton sheet using a strong solution of RS glue (42 grams to half liter of distilled water). I would have used linen but economics are a factor at the present moment thus I'm hoping for a good adhesion between fabric and panel as well as good protection from the gesso. My main interest was to have some extractable layer available for later if it is ever needed.

I'm leaving a few panels unfabric-ed so as to compare the difference.

Thanks again for your book, I've been reading and studying it. It is very helpful because it contains distilled experience - which also coincides with my own.
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  #6  
Old 09-06-11, 04:24 PM
Silver Lining Silver Lining is offline
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Great feedback, Koo.

Here in the U.S., it is almost impossible to get double sided untempered hardboard but I have been able to source double sided tempered h.b. that is made without formaldehyde. I know formaldehyde is bad stuff because three weeks ago I had a very bad cough and it was from all the formaldehyde off-gassing from the Russian Birch cradle strips I had piled up in my studio. I got rid of them and went to formaldehyde-free strips and my coughing went away.
I am in the proccess of experimenting with the tempered panels by sanding them and applying a 'coarse' muslin over them to see if that helps prevent any cracking and/or compatibility issues.

One question I have is, since I pre-cradle/brace my panels, if I coat the back with R.S. glue, will this help reduce moisture intake through the back of the panel or is it a waste of time? My panels are too big/cumberson to gesso all the sides/back.

Ellen, how did your panels work out?

Thanks,
Silver



Quote:
Originally Posted by Koo Schadler View Post
Hello Ellen,

A few thoughts on your question. First, my understanding is that the oils used in tempering hardboards are drying oils - meaning that they cure, or polymerize, over time and are then irreversible (can't go back to being gooey). This makes sense, as I don't think a manufacturer would want non-drying oils - they might not only leach into a painting but, more important to the manufacturer, might also pose a problem for a builder, their primary customer. So if this presumption is correct, that the oils in tempered boards are drying oils and cure, I don't think there is any worry of them traveling into your gesso or painting.

However tempering oils, even drying ones, might interfere with the adhesion of gesso to the surface. Additionally, some hardboards and MDF are tempered with wax, which could also affect adhesion. So I do think there could be a problem in that regard.

How long before a problem, such as separation between gesso and panel, arises? Maybe in a few years, maybe in fifty, maybe never...these archival questions can be hard to answer because there are so many variables (how much and what type of tempering is in the panel, how well is the surface prepared, how strong and well made is your gesso, what conditions does the painting live under, etc). The other relevant issue is, how long do you want your painting to last? Some people care about their work being archival, others don't.

My guess - and truly it is a complete guess - is that if you prepare your support well (more on that below), make high quality gesso, and store the resulting painting under favorable conditions, it would probably last for a pretty long time... a lifetime or two, if all the variables were favorable?? Totally a guess. It is only to say that tempered hardboard or MDF are not necessarily deal breakers if one is diligent in other regards (and I say that as a devoted fan of the UNtempered variety).

To prepare a hardboard or MDF support well, here are some suggestions: 1. Lightly sand the panel to lift off any stray nubbins of anything that may be stuck to it, as well as to open up the surface (so use sandpaper with a bit of tooth, such as 180 grit). 2. Next rub it down with denatured alcohol to remove greasy fingerprints. 3. For your first layer, rub in a coat of rabbit skin glue and let that dry overnight, before applying the gesso layers. 4. Make a great gesso! (i.e. use the best glue you can find, don't overheat it, etc).

There is one more relevant topic in regards to MDF boards which is that sometimes, I believe, they contain formaldehyde. I don't think there is any question that overexposure to formaldehyde is bad for one's health, but I'm not sure how long a panel will out gas. Indefinitely? Or just for a few months after being made? I don't know..out gassing may be a mute point by the time it enters your studio, but maybe not. And will out gassing, if it actually does continue to occur, affect your painting (as well as you)? I don't know that either. Perhaps one of the chemically savvy posters out there can tell us more.

Eric Thomson wrote an informative article on hardboard that addresses some of these issues. Its several years old by now but still relevant. www.truegesso.com posts it on their website, at:

http://www.truegesso.com/~truegessol...%2011-6-08.pdf

Good luck.

Koo

PS - Love your gesso/moisture theory DLH. I buy it. I'm sure you also know that another one of the magical properties of gesso is that its alkaline nature beautifully counters the acidity of wood. What a substance....
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  #7  
Old 10-06-11, 12:50 PM
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EllenT EllenT is offline
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Default using MDF anyway...

Silver Lining,
Well, good you asked. I just finished gessoing 4 MDF panels. I pre-sanded all of them and glued (with a relatively strong RSG solution) a very thin piece of fabric on to 2 of the panels (on both sides), leaving the other 2 without fabric as a test. Then proceeded with my gesso (both sides and edges) - which BTW - also worked out very well since I had been having problems with that, too.

Now all 4 (unpainted) panels look and feel very good. The fabric-ed ones have just a bit more texture, which might have been avoided by doing more coats of gesso but I stopped at 8 coats and called it a day.

In retrospect, I would do a coat of size to the panel before applying fabric just to insure good adhesion if I were to do this procedure again in the future (so I'd recommend it to you). My whole reason for doing this fabric treatment was to simply provide a way to save the painting should the ground separate from the MDF panel at some point in the future.

I can also say that I have noticed (in the past) a positive (to me) difference in the way egg tempera handles on boards that have been covered with fabric first before gessoing. There is a certain kind of springy-ness, just a tad of softness in a way that otherwise I can't really describe. I find unfabric-ed boards that have been gessoed a little "hard", lean or stiff. But these are subtle nuances...
Good luck to you.
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  #8  
Old 10-06-11, 10:22 PM
Silver Lining Silver Lining is offline
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Thanks Ellen.

How large are your panels? Would you recommend the same solution strength for the size as well as gluing down the panels? When you put size on, do you let it dry over night?
I bought a little coarser cotton thinking it would be closer to linen and since my panel sizes are 'large' (30" x 40").
When you glue your fabric on, do you slowly apply it as you put down your RS glue or just paint the glue on and apply the cloth?

-Silver

Quote:
Originally Posted by EllenT View Post
Silver Lining,
Well, good you asked. I just finished gessoing 4 MDF panels. I pre-sanded all of them and glued (with a relatively strong RSG solution) a very thin piece of fabric on to 2 of the panels (on both sides), leaving the other 2 without fabric as a test. Then proceeded with my gesso (both sides and edges) - which BTW - also worked out very well since I had been having problems with that, too.

Now all 4 (unpainted) panels look and feel very good. The fabric-ed ones have just a bit more texture, which might have been avoided by doing more coats of gesso but I stopped at 8 coats and called it a day.

In retrospect, I would do a coat of size to the panel before applying fabric just to insure good adhesion if I were to do this procedure again in the future (so I'd recommend it to you). My whole reason for doing this fabric treatment was to simply provide a way to save the painting should the ground separate from the MDF panel at some point in the future.

I can also say that I have noticed (in the past) a positive (to me) difference in the way egg tempera handles on boards that have been covered with fabric first before gessoing. There is a certain kind of springy-ness, just a tad of softness in a way that otherwise I can't really describe. I find unfabric-ed boards that have been gessoed a little "hard", lean or stiff. But these are subtle nuances...
Good luck to you.
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  #9  
Old 11-06-11, 04:01 AM
Silver Lining Silver Lining is offline
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How big are your panels? Did you use the 42 gram to 1/2 liter RS glue solution for everthing (including the gesso)?
Thank you,
-Silver

Quote:
Originally Posted by EllenT View Post
Silver Lining,
Well, good you asked. I just finished gessoing 4 MDF panels. I pre-sanded all of them and glued (with a relatively strong RSG solution) a very thin piece of fabric on to 2 of the panels (on both sides), leaving the other 2 without fabric as a test. Then proceeded with my gesso (both sides and edges) - which BTW - also worked out very well since I had been having problems with that, too.

Now all 4 (unpainted) panels look and feel very good. The fabric-ed ones have just a bit more texture, which might have been avoided by doing more coats of gesso but I stopped at 8 coats and called it a day.

In retrospect, I would do a coat of size to the panel before applying fabric just to insure good adhesion if I were to do this procedure again in the future (so I'd recommend it to you). My whole reason for doing this fabric treatment was to simply provide a way to save the painting should the ground separate from the MDF panel at some point in the future.

I can also say that I have noticed (in the past) a positive (to me) difference in the way egg tempera handles on boards that have been covered with fabric first before gessoing. There is a certain kind of springy-ness, just a tad of softness in a way that otherwise I can't really describe. I find unfabric-ed boards that have been gessoed a little "hard", lean or stiff. But these are subtle nuances...
Good luck to you.
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  #10  
Old 11-06-11, 04:15 PM
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RobM RobM is offline
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Just picked up on this thread........I have been using MDF for well over 20 years and the only problems I have encountered was a little warping. I'm afraid that European MDF does contain formaldehyde so only sand or cut outside or wear a mask. I have a tendency to sand the front surface about 5mm from the edge to a slight bevel. When gessoing I also gesso the sides as well as the back. There is a slight moisture absorption when gessoing the sides and there is a tendancy for the panel to swell a little thus the 5mm slight bevel. I found by not producing that'bevel' when sanding the gesso I would get down to the MDF at the edge. (Hope I have explained myself....)
I work on panels from quite small and occassionally up to 1200mm x 900mm (approx 4' x 3').
I have never used a fabric and so far none of my customers has reported any problems. I have a number of works well over 20 years old and they also have no problems.
Rob
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