Notes from a wet wall

[preservator]

Three frames were removed from a damp wall, recently and mold had appeared, in conjucntion, with each. The frame that had a foam centered backing board and no edge taping had mold growth on the front of the window, with staining throughout.
The same thing was true of the frame that had had the edges of its mat/glass package taped with masking tape (which had released its grip on the glass). The frame with a plastic backing board had mold growing on the wall behind the frame, but none visible in the frame (that frame has not been opened).



Hugh

 

[Dave]

Thanks for sharing this story, Hugh. I would deduce that it's best to use polyflute board as a finally backing before applying the dust cover.

Another example of the changing methods of practical real life framing.

 

[tedh]

Trouble is, polyflute has gone was up in price. A 4x8 sheet that not long ago was $11, more than doubled in price last summer due to the oil price spike. More bad news for our customers.

And, by the way, the prices have not dropped this winter. What a surprise.

Back to the mould: around here we have a lot of old houses with little or no insulation or vapor barriers. Temperature change and condensation is considerable on south-facing walls. Coroplast really helps.

 

[Joe B]

Hello Hugh,

Thanks for the information. I am a little curious. Which part of the country was the home located, how old was the home, what room in the house were the three frames hung in, how long where those pictures hung in the same spot, was there other excessive dampness to any other wall, and finally, what would you suggest as proper steps in framing as a cure for this type of problem?

Joe

 

[Baer Charlton]

4mm CoreX $11, 6mm $11.80, 10mm $12.50 delivered. tedh, you may be buying from the wrong supplier. And if I order 10 sheets and pay COD -7%

 

[tedh]

4mm CoreX $11, 6mm $11.80, 10mm $12.50 delivered. tedh, you may be buying from the wrong supplier. And if I order 10 sheets and pay COD -7%

This was a trusted supplier. Time to look elsewhere.

 

[SusanG]

Would a tyvek backing have helped to keep out the dampness?

Susan

 

[preservator]

This home was in the mid-atlantic area and was built in the '50's, to the highest standards. The evidence we can see from mold growth suggests that a plastic backing board or dust cover would provide some protection, beyond that afforded by the paper/plastic board. The paper, on the latter board, serves as a wick and will transmit moistue, even under a tape layer, making it less of a barrier.


Hugh

 

[Jim Miller]

After noodling this story for a while, I have a couple of thoughts and would like your opinion. I know it's not your nature, Hugh, but it's OK to be blunt here.

You've made it clear that a non-hygroscopic backing would provide the best moisture barrier, such as polyflute, Marvelseal, sheet acrylic, or glass. But if the edges of a non-hygroscopic backing board were left open, moisture could migrate into the frame package at the perimeter. Right?

If the non-hygroscopic backer were sealed to the back of the frame by foil rabbet-lining tape or even a plastic tape, the migration would be more effectively slowed. And if the entire frame package were sealed between the glazing and that backer by a gas-impermeable barrier such as foil rabbet-lining tape or Marvelseal, the migration of moisture would be most effectively slowed -- maybe even stopped altogether. OK so far?

A dustcover is generally used in order to close up the back of the frame and keep the interior clean, but it becomes unnecessary for that purpose when a non-hygroscopic backing is used, especially if it is well-sealed at the edges. In that case, the dustcover would be only decorative.

If a paper dustcover were added on top of a non-hygroscopic backer, that would cover the whole back surface with a moisture absorber. It would seem that if there were any route for moisture migration into the frame, the dustcover paper would provide a conduit for it.

Am I correct in concluding that the frame described would be better off without the dustcover?

 

[preservator]

Jim has given us lucid and well-reasoned look at the physics that frames encounter, in such a trying setting. A paper dust cover can gather mositure and may not be useful if a plastic backing board,with internal sealing has been used. A plastic dust cover that stays bonded to the frame should ward of water from the back, but keeping anything sealed in a frame, where that seal depends on pressure-sensitive adhesives is likely to encounter problems, five to ten years out. A Tyvek dust cover bonded with hot melt should stay in service, indefinitely, but that is an expensive option for the framer. There are no simple or right answers to these questions, but careful consideration, such as Jim has shown, gets us closer to solutions that work.


Hugh

 

[Bob Doyle]

I think that while what Jim said may be true, and that a polyflute backing is better than fomecore, backing paper or cardboard, I do have a problem making a definitive statement to that effect becuase Hugh, you didn't open that frame and inspect it.

The frame with a plastic backing board had mold growing on the wall behind the frame, but none visible in the frame (that frame has not been opened).

The sentence "none visible in the frame" just really means you didn't see any problem. I've had many a frame that needed refitting and saw "no problem" with the framing, only to open it up and find the image glued down to an acidic board!

 

[Jim Miller]

Bob, Hugh said he did not see evidence of moisture damage, which has nothing to do with the possibility of improper mounting.

 

[Bob Doyle]

I was just trying to point out that not seeing damage doesn't mean it isn't there. Hugh knows what he is doing, and is far better than I at evaluating water damage and mold intrusion. I was just trying to say that without actually opening it and seeing first hand it would be difficult to judge the presence or lack of the presence of mold.

I respect Hugh's skills, and would have prefered a definitive statement that coroplast is better. But without objective data, opening the frame, it is a subjective opinion. Granted one based on experience, but with coroplast being new (ish) for many of us as a substrate facts would be appreciated, and help us inform our customers' and our buying decisions.


A related followup. We know that glass can have water condensation develop on it. We know that fomecore can absorb water, but since coroplast doesn't absorb or wick water, is it possible for water to condense on the inside of coroplast and potentially introduce water to the artwork from the back?

 

[Jim Miller]

...since coroplast doesn't absorb or wick water, is it possible for water to condense on the inside of coroplast...?

Condensation would probably be possible on the warm side of nearly any sheet products we could put into a picture frame. The main difference is that some sheet materials, such as glass or metal, condense moisture quite readily. Sheets with poor thermal properties do not insulate well. That is, a temperature change can quickly permeate through the sheet. When temperature changes very quickly, condensation forms on the warm side. Thickness of the sheet affects that, too.

Other sheet materials, such as plastics, have better thermal properties, which slow down the temperature permeation through the sheet and thereby reduce their tendency to condense moisture.

Fluted polypropylene (aka polyflute, aka Coroplast brand) is plastic and, like all plastic sheets, has better thermal properties than glass. That is, it's a better insulator than glass. But polyflute also has another advantage in its construction. Having two walls with air in between further enhances its ability to slow permeation of a temperature change, and further improves its resistance to condensation.

The expanded styrene core of foam core would also be a better insulator than glass, but I doubt that it is s solid sheet, and wicking of the paper covers is an issue.

...I think.

Any corrections, Hugh?

 

[Robert Shirk MCPF]

A little info from the Tyvek website...

GOOD LIQUID BARRIER PROTECTION
Spunbonded Olefin with neither corona treatment nor antistatic agent (e.g., Style 1073B) has a hydrostatic head in excess of 50 in. (127 cm). If antistat is applied, the hydrostatic head will drop to 40-50 in. (102-127 cm). Corona treated and antistated Spunbonded Olefin (e.g., Style 1073D) has a hydrostatic head that is less than 15 in. (38 cm).

EXCELLENT MOLD & MILDEW RESISTANCE
Although mold and mildew can grow on Spunbonded Olefin, it shows no degradation after being buried in soil for an extended period. Clean Spunbonded Olefin will not promote the formation of mildew.

For more info look here...

http://www2.dupont.com/Tyvek/en_US/index.html

 

[preservator]

This thread has produced just the sort of exchange that forwards our craft. Both polyflute and foam centered board are valuable products and understanding how they behave in trying conditions allows us to use them best. The paper on the foam centered board can wick mositure and cause warping, but the flutes in polyflute (and any other fluted material) are a fire hazard (fortunately, since here it is next to the wall, that threat is minimized), but both are excellent products and have an improtant role to play in preservation. As Bob notes, the interior of the frame with the plastic backing was only observed from the outside. It is worth noting that the mold grew on the wall, which suggests wall board construction, where the paper gives a food source to the mold.


Hugh

 

[Finest Fabric]

The use of Tyvek as a dustcover in high humidity/moisture environments has always confused me - isn't one of its advertised properties that it allows moisture vapor to pass through? OK it does not act as a wick, but if it allows moisture into the frame package there are presumably materials inside that may. Would the "breathability" of Tyvek prevent this?

I frame numerous pieces each year for peoples boats (always with a caveat). This has to be one of the most punishing environments for framed art. I would think that the best solution here would be to frame the piece in a reasonably temp/humidity controlled environment, seal, and back with a product that is as impervious to moisture vapor as possible. Wouldn't the use of Tyvek here allow the "innards" of the frame package to be exposed to moisture vapor?

If I'm right about using an impermeable backer, are there any products out there in sheet form that could be used? Is Mylar (or other films) impermeable?

-Bryan

 

[Sherry Lee]

This is a wonderful thread!

One thing that kept coming to mind as I read.....as part of our role, we are to educate our customers of the importance to have their valued framed art examined regularly. This thread tells me to remind them even more often and when the framed art is placed under stressed conditions, it should be examined even more often yet! This becomes the owners responsibility to actually do it, but our responsibility to not fall short on education.

 

[Kirstie]

How long had the frames been on the damp wall?

Interesting thread--thanks.

 

[Joe B]

Kirstie - how long were they on the wall was one of the questions that came to my mind too. I believe the environment of the hung art is important - were these hung in a bathroom, sauna, atrium, living room, cold outside wall? When was the last time they were opened up to check and clean the contents. This location of hanging could be very conducive for moisture and mold. I believe that you have to frame a piece of art with the hanging location in mind. What I frame for a person to hang in a lake cabin is going to be different than how I will frame something that is going to hang in a year round home with a controlled environment. This is a good thread because it is giving me some different ways of looking at how I should be framing some items.

 

[Prospero]

One thing that hasn't been mentioned in this topic: Bumpers.
If the lower edge is off the wall, air currents can circulate and you don't get an area of stagnant air building up behind the frame.

 

[QuickDraw]

Just something to keep in mind as you frame such items for such conditions. In the case mentioned here, the moisture came from the atmospheric conditions of the room. In this case, a sealed package with a proper moisture barrier would probably have reduced the chance of the mold.

However, keep in mind that, as someone briefly acknowledged above a sealed package has the atmospheric conditions present in your shop at the time it was framed. If it is truly sealed, these conditions will not change in regards to moisture and air content. Most comfortable conditions are somewhere near 70 degrees F and 50% RH which means the air in this package has a 50 degree dewpoint. If it is completely sealed, as soon as any surface on the inside of the package reaches 50 degrees F condensation will begin to form. If for some reason your humidity level in the shop is higher your dew pt will also be higher. I would think for houseboats, cabins, lakehouses, etc... indicating that this would be a dangerous gamble as well. If the package is sealed to older standards, the conditions in this environment will also change to meet the conditions of the room, albeit a bit slower. Not saying either method is correct for all situations, you just need to be educated about what causes the condensation and create your frame packages to minimize the customer's chance of risk. I'd say if they're hanging on an outside wall, the poly backing with a lined tape seal is probably a good choice... Condensation will probably start on the tape... Why??

 

[Jim Miller]

...Most comfortable conditions are somewhere near 70 degrees F and 50% RH which means the air in this package has a 50 degree dewpoint... If it is completely sealed, as soon as any surface on the inside of the package reaches 50 degrees F condensation will begin to form. If for some reason your humidity level in the shop is higher your dew pt will also be higher.

In Hugh Phibbs' class about sealed frames, he discusses the frame's closed-up environment. As needed, the hygroscopic materials in the frame package may be warmed to reduce moisture content. Trouble is, most of us do not have a reliable way to measure moisture content in the boards and papers, or to know when the moisture content has become suitably regulated.

...... Condensation will probably start on the tape... Why??

Which tape, and why would condensation form on it?

 

[QuickDraw]

Which tape, and why would condensation form on it?

If you seal the frame with the metal lined tape, I would argue that the condensation would either first form on the metal surface or the glass. Most likely the tape because it is thin, not insulated, and the metal is a good conductor of heat and a very poor insulator... It will likely be the first surface to reach the condensing temp.

 

[Jim Miller]

..I would argue that the condensation would either first form on the metal surface or the glass. Most likely the tape because it is thin, not insulated, and the metal is a good conductor of heat and a very poor insulator... It will likely be the first surface to reach the condensing temp.

Dew point is the temperature at which the air is saturated with moisture. I'm no expert on dew points, but my first thought is that indoor humidity is not usually high enough to saturate the air.

You mentioned that with an air temperature of 70 deg.F and relative humidity of 50%, the dew point would be 50 degF.

In order for dew to form on the the foil/paper tape you mentioned, with air temperature of 70 degF and 50%RH, the temperature of the tape would have to be 50 degF, a difference of 20 degF.

As you said, the tape is a poor insulator and would react very quickly to a change of temperature. In real world conditions, if the room temperature dropped 20 degrees in, say, 15 minutes, the tape's surface temperature probably would adapt before dew could form. That is, it might be extremely difficult to make the tape surface 20 degF cooler than the air temperature in any indoor climate.

Now, consider this common, real world scenario for a picture frame:

The room temperature has been 73 degF for hours, as is the internal temperature of the frame, and the surface temperature on the frame's glass. Through a west-facing window, the afternoon sun suddenly begins glaring onto the glass. The room's air temperature remians at 73 degF, but within minutes, due to radiation of the sunlight through the glass, the temperature inside the frame could rise to 95 degF. And at that point, moisture would condense inside the frame.

Here's another:

In winter, temperature in the gallery is 70 degF @ 35% RH; dew point temperature is 40 degF. Frames in the room are fully acclimated. Customer picks up her framed art and puts it in her trunk @ about 35 degF. Within seconds the outside of the glass cools to a surface temperature of 40 degF and condensation forms inside the frame.

 

[QuickDraw]

Agreed Jim,
The only word of caution that I'm trying to get across is that if you actually are able to seal the frame package completely, there is no adjustment. That means that if at any time, the package drops below the dewpoint in your shop, water will condense. While I realize this is somewhat improbable, every time we find a way to better insulate and isolate the package, we are in fact increasing the time required for the package to equalize with the room. This may be good, and it may be bad. You have to determine for yourself. The construction industry had to deal with these issues a while back as the insulating materials they used improved. Their solution was double pane glass with inert gas between them. I don't think we will be doing that but it may have an application. More importantly, I would not want anyone to think that completely sealing the package is the do all be all solution to framing problems. Along with each solution comes a new set of problems. Just trying to bring up some that might be coming along...

 

[Jim Miller]

... if at any time, the package drops below the dewpoint in your shop, water will condense...

OK, but how likely is that? In most cases it's all about the rate of temperature change inside the frame.

High humidity and air/surface temperature differential are both essential to the condensation of moisture, which occurs on surfaces considerably warmer than the air around them. Creating dew in a normal room may be possible, but that would be unusual -- and uncomfortable for occupants.

As air temperature in the room changes (cools), surface temperatures in the room would probably acclimate fast enough to avoid the dew point differential. The air temperature shift would have to happen very, very quickly. The larger the volume of air in the room, the more difficult it would be to create a dew point condition.

Just as a room is a closed-up environment, so is a picture frame. As in a room, humidity and air/surface temperature differential within the frame package are the factors that matter.

If the relative humidity inside the frame package were 50%, then a temperature differential of about 20 degF would be needed in order to condense moisture. Lower RH would require greater temperature differential; for example, if the RH were 30%, a temperature differential of about 35 degF would be needed.

A major benefit of a well-closed frame package is that is slows the rate of temperature change inside. In a frame with tight-fitting glazing, insulating filler boards and a tight, non-hygroscopic dustcover, the rate of change would be slowed and condensation inside would be less likely. A completely sealed frame would be even more effective in slowing the rate of change inside. An open frame, on the other hand, would be least effective in slowing the rate of change inside.

Now, if the frame were moved suddenly to a much cooler environment, condensation would be likely (warm gallery to car's cold trunk in winter). Condensation would also be more likely if interior temperature of the frame were suddenly warmer than room air (radiating sunlight through the glass).

 

[preservator]

As confusing as dew point issues are, a simple test can be illuminationg. Take a mat, conditioned to 50% RH at 70 degrees F and glaze it and seal it thouroughly
(using metal/plastic foil and tight adhesive) and then place it in a refridgerator. Check for condensation, within. When the package comes out, if it is not held at 60 degrees, for 24 hours, it may have condensation on the outside. Matting materials, at proper museum conditions, have but a few drops of water in them and a great capacity to hold moisture, which means that they can buffer a package against large temperature swings. Condensation seen on the inside of glass, usually comes when the contents of the frame are too damp and sun light goes through cool glass, without warming it and warms the matting materials, casuing them to give up moisture, to the air, which is what condenses on the glass.
The frames had been on the wet wall for long enough for the pink tones in a pastel to fade, completely.


Hugh

 

[QuickDraw]

Ok, Hugh I'll take your answer, in that the mat, foam, and art act as a buffer and absorb the condensate that comes fromthe air, when the temperature drops below it's saturation point. This will allow the package to somewhat equalize and not show the condensate in most places. I still think that if you are going to leave the art in an area that is dry, but temperatures may vary (such as an empty vacation home in the mountains), it may be best to not seal the package to atmospheric conditions as the humidity level in your shop is likely to be higher than it is in the natural environment. Instead, if your customer is concerned about moisture and potential damage, the framer needs to make sure they educate themselves and make an informed decision..

By the way when 70 deg 50% RH drops to 50 deg it does not equalize to 50 deg 50% humidity without mixing air or losing water. It drops to 50 deg 100% humidity. It's a law of physics not an opinion. The humidity level is strictly an indicator of how much moisture is in the air. There are shops out there that during the summer may find interior conditions to be 80 deg 90% humidity. If that air is sealed inside a frame, it will produce moisture at some point and that is a mathematical certainty. As I have stated several times, I am only trying to make sure that people do not apply a tool blindly without understanding the complete picture....



I agree whole heartedly that the principles of sealing and

 

[preservator]

Practical issues that come up with sealed packages, in service:

moisture will leak through acrylic sheet, which means that a package left in a dry climate will warp inward, toward the properly conditioned (now more moist) interior

as mositrue leaks throgh acrylic, the interior of the package will dry below 50% at 70 degrees F, which means that package designed to be used with very wet or dry spaces, should be glazed with glass

the 50/70 setting is only one which people prefer- it is a compromise between wetter conditions which some wood and ivory do well at and much drier conditions, which are best for metals

sealing protect against pollution and pests, as well as bad climate.



Hugh

 

[Jim Miller]

...during the summer may find interior conditions to be 80 deg 90% humidity. If that air is sealed inside a frame, it will produce moisture at some point and that is a mathematical certainty.

Of course it would. At 75 degF and 90% RH, the dew point would be 72 degF. At 75 degF and 80% RH, the dew point would be 68 degF. With temperature differentials of only 3 to 7 degF, condensation certainly would would be likely.

It would be unwise and unnecessary to seal such high RH into a frame. The hygroscopic materials could be conditioned to a lower moisture content before fitting, and a little while in a heated drymount press would take care of that. A moisture meter would be handy to test moisture content, such as this one:
http://www.engineersupply.com/ProductInfo.aspx?productid=ES150&affid=16

Another strategy would be to close up the frame temporarily with a hygrometer inside, and check the RH inside the frame after a couple of days. If it is acceptable, remove the hygrometer and seal it.

Accuracy is not crucial here. If you know the RH inside the frame is in the range of 50%, plus or minus a few points, that would probably be sufficient for the consumer world.

 

[QuickDraw]

Agreed, and I realize that you or Hugh either one would recognize that, but not everyone understands thermodynamics and the impacts that it can have on the situation. I have seen many well intentioned guidelines turn drastically ugly over the years, because people did not understand what they were really dealing with. Remember this forum is open to the public, and not everyone who reads here understands hygroscopic design or thermo. I would suspect many do not... That's left to those unreasonable engineers, their slide rules, and tape measures....

 

[nona powers]

Better to be safe than sorry

The reason I think there is no better or best to framing standards is illustrated by this topic. As framers we learn more every day, in fact I'm going to do a post on how far we have come, but we cannot know it all. I am not Hugh, (DARN), will never know as much as him but I do know enough to find help when I need it. If I don't feel confident practicing a certain technique, I will find someone who can educate me, or do it for me. I consider that an important part of being a custom framer. Knowing when and when not.