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How To Remediate Water Damaged Paper Records

Uncategorized Mar 04, 2022


Hello, and welcome to the Mould Show. My name's Dr. Cameron Jones. I'm an environmental microbiologist, and for any of my listeners and viewers here in Australia, you are probably all aware of the catastrophic weather conditions that are affecting Queensland and New South Wales. And for many people, they have suffered devastating impacts caused by this floodwater. And for all the people who watch my show, you know that I'm particularly concerned about the impact of water damage on personal property and the potential for mould and mould exposure to not only damage your assets but cause unexpected or hidden health risks and consequences. So, today we're going to be focusing on what you do if your precious documents, your paper-based documents become water damaged. What are you going to do? Are you going to get out the hairdryer? Are you going to attempt to move them obviously to a dryer location?

 But what happens if you come back to your property, or your residence, or your car even, and some of your paper documents are water damaged? How best are you to deal with this to firstly, make sure that they don't become a reservoir of mould or hidden mould that you could potentially transfer from one location to another? And so, that is the topic today. So, today we're going to be talking about do-it-yourself mould remediation of paper documents, and to get into this, I want to set the scene. Obviously, I have found an academic paper which is focusing on this topic, and they are explaining the best practice to minimize mould and control mould on paper documents. So, just think about documents like wills, precious records, lists of passwords, as well as books and other potential items like that. So, what are we going to be doing?

 Well, here is the publication, and it came out very recently, and the focus of this paper is sterilization of paper during a crisis. And the interesting focus of this particular publication was, and we're going to be going through this, and I'm going to be showing you some of the fine detail about this. But what these scientists were looking at is that they were looking at how you would deal with damage to paper-based documents during the COVID 19 pandemic. And obviously, we all know that that was a significant focus of attention for the last couple of years, but certainly, water damage is, in my opinion, much more likely to cause a significant impact to paper-based documents. And this publication is the one that explains firstly, what to do. What does the science actually say? And I'm all about following the science.

 So, if we track through this publication as I'm going to now, I'm going to be talking to you and explaining how you can treat your own documents yourself. And to do that, I'm going to move away from the abstract. Again, all of this information is going to be in these show notes, and to just make this very clear, when we're talking about microbial damage to paper documents, there is a pyramid that reflects the difficulty with which you can kill these microorganisms which may start growing on your water damaged paper belongings. And so, in terms of resistance, obviously fungi are in the orange band and they are, of course, something that is difficult to kill. And so, we need to be aware that the spores are in fact, the most difficult to kill.

 And when we're talking about this, and we're talking about sterilization, there're essentially really only a couple of ways in which you can successfully disinfect or sterilize paper documents, and the most common one is called gamma radiation. Now, most of us don't have access to this cold sterilization technique, which uses radioactivity. Now, it works, but most of us, apart from libraries and archivists, don't have access to this technology. So, what are we going to do? Most of us think of moving to the hairdryer, for example, or spreading out all of your documents in front of a heater, and that, of course, may work to a great or lesser extent, but what does the science say? So, if we move into this publication, and I'm going to go through here, what these scientists did is that they were looking at various different types of methods to decontaminate documents, and they focus on these twin approaches of gamma sterilization.

 And as you can see here, using with the arrow and oven equipment, so just a normal oven, and what these researchers were doing is that they were building on some other research that had already been done, and they were asking this simple question. What is the best temperature to set your oven at in order to get rid of these offending microbes that are growing to a greater or lesser extent on your water-damaged paper documents? So, if we go through, and I go through and summarize exactly what the experiment is doing, is that the scientists were testing two different sterilization methods. Number one, the gamma sterilization, which we know works. It generally achieves a hundred percent kill threshold, but for all of you who are potentially dealing with these water-damaged documents, all of us have an oven, and you may need to resort to using an oven for some of your precious documents that you need to recover and ensure that they don't become seriously mould contaminated.

 So, the second part of the experiment that the scientists were looking at is what is the impact of dry heat? What is the temperature that you should set your oven at? How long should you keep the documents in the oven and what is the structural damage to the paper after these types of treatments. And obviously, the scientists were interested in the microbial count. That is, how many microbes were left on these documents after they were dried, and then they used a scanning electron microscope to examine the fine structure of the paper documents. And I'm going to be drilling into some of this data as well, and showing this to you and just to show you exactly what the oven looked like that the scientists used, they used a forced convection drying oven. Now, this is not dissimilar to the type of oven that you have at home probably.

 And so now, if we look now at the first evidence because I have to show you what the impact of gamma sterilization is on your documents. And so, the scientists, of course, took some squares of paper, submerged these in water, and looked at the different types of fungi, gram-negative and positive bacteria, and looked at the inactivation of these microorganisms after sterilization with gamma radiation. Now, look at the right-hand column, and you can see that for the bacteria and the fungi, they use Candida Albicans as their test microorganism. They were able to achieve a 100% kill threshold. Now, you would expect this as the outcome, really essentially from first principles because this is a known fact from physics. Now, you're probably wondering though what the impact is for the dry heat sterilization. What could you, or what should you set your domestic grade oven at to replicate the success shown in this paper?

 And I'm going to show that to you now. And so, what these scientists did is that they tested three different temperatures, 15 minutes, 30 minutes, and 60 minutes. And I have highlighted certain elements of the table in the document that they, or the paper that they published, and you can see in the right-hand column, that after 15 minutes for fungi, they achieved a 97.1% success rate at a hundred degrees celsius. If they increased the temperature of the oven to 150, they increased the ability to decontaminate the microorganisms or fungi. And at 200 degrees, they were able to kill all of the microorganisms.

 Now, if I just zoom out and you can see that it's 60 minutes, obviously leaving the documents in the oven for a lot longer achieved a hundred per cent kill, but what is the impact on the ultrastructure? How did this impact on the structural integrity of the paper? Now, I'm going to go through that in a moment, but I want to highlight what I recommend after reading this peer-reviewed publication is to use 15 minutes of dry heat at a hundred degrees celsius achieved a 97.1% kill threshold against fungi on wet paper.

 Now, I think that that is an outstanding result. This publication is going to be available in the links in the description to this live stream or podcast, and it will be retrievable after the live stream from my YouTube channel.

 Now, I want to have a look at some of the SEM results because they are in fact a little bit different. Now, I'm going to quickly go through this because the scientists have shown the impact of gamma sterilization on the ultrastructure of the paper. And as we all know, paper has cellulose fibers in it which are derived from pulp, which is itself derived from wood timber. And essentially, there is differences, obviously, by affecting paper documents that have been water damaged with both gamma radiation, as well as dry heat. And you can see in the SEM micrographs, the scanning electron microscopy that the paper structure after exposure to dry heat, the control is in panel A.

 And so, this is the control here, and the different heat impacts are shown respectively in B, C, and D at a hundred degrees celsius, which is the one that I'm advocating. And then you can see 150 degrees celsius, and then at 200 degrees celsius. So, the lowest impact on damage to the paper structure is really achieved at a conservative temperature of a hundred degrees celsius. And in fact, this is what the scientists conclude as well, that if you want to achieve sterilization efficiency, you will have to heat it at either a higher temperature for longer, essentially. But if you want to achieve a reasonable balance between damage to the paper and achieving a good kill threshold, I think 97.1% kill threshold is a good balance in the middle. So, therefore, that is achieved at 15 minutes of dry heat at a hundred degrees celsius.

 So, that is the key message that I want to convey to you this week because there are many thousands of Australians who are suffering with this water damage to paper documents. Now, I'll probably make this a dedicated live stream as well, but what about damage to your mobile phone or to computers? I would suggest that you purchase some Desiccant crystals and consider placing your iPhone if it becomes damaged, or any of the other range of cell phones that you may have yourself, and put this in a sealed container with Desiccant. There is all sorts of different ways in which the phone itself will tell you if it has been water damaged, and you may not be able to get the water out yourself. So, the Desiccant crystals is perhaps the best suggestion I can give you. The recommendation is not to use rice, which is one of the methods that is touted online as being an effective way of salvaging your electronic phone if it has become water damaged but definitely do not use a hairdryer.

There is some excellent publications looking at the impact of clean water damage to other items of consumer electronics, such as computers. And the key thing here is to unplug them from the power before you do anything. Certainly, for computers and desktops, the recommendation is to turn them upside down so that they can drain. Take off the case if you can, and disassemble what components you can so that you have the best chance of allowing this water to evaporate. In any case, as I said, that is probably going to be the topic of another live stream where I will bring you some more evidence out of the literature that talks about best practices for salvaging home electronics that have been water damaged. But in all cases, be careful with anything that plugs into the power if it has been and water damaged. But for paper-based documents, an oven could be your best friend. Anyway, see you next week. Bye for now.

Watch the Livestream:


Alshammari, F.H., Hussein, HA.A. Sterilization of paper during crisis. AMB Expr 12, 13 (2022).


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