This presentation is part of the Facebook live video, March 23, 2020.

Dr. Mary Striegel:  Today’s topic is COVID – 19 virus basics and we are going to talk about disinfecting cultural resources.

I’m Mary Striegel, I am a conservation scientist with about 25 years with the National Center for Preservation Technology and Training.  I’ll be talking to you today about isolating, cleaning, or disinfecting historic materials.

The discussion that we are going to have today is based on the best available current knowledge but as you know COVID 19 and the Corona virus situation is rapidly changing and rapidly evolving situation. And so, while I am providing you with information now that information may change with time. If we do have updates I’ll post it on Facebook and I’ll get back to you and we can talk about what we need to do next.

There are five Questions that I’m going to try to answer for you today.

  1. The first question is what is the Covid-19 virus?
  2. Second, how long does it persist on surfaces?
  3. Third, how do we deactivate the virus?
  4. Fourth, what about historic materials?
  5. And fifth, what safety precautions do we need?

This live broadcast is going to be recorded; it will be transcribed and available to everyone on our website at a later date.

So, what is the Covid-19 virus?

Well, it is a Coronavirus. That means coronaviruses are named for their appearances under a microscope. And so the viruses look like they are covered with pointed structures around them like a corona, or a crown. There is not a lot of data on this particular corona virus but there is information on similar viruses that can help us better understand this one.

All viruses are bits of genetic code or RNA that are bundled inside lipids and proteins and then it has an exterior fat-based envelope, casing known as a viral envelope. It’s this fatty envelope that elects the corona virus be susceptible to soap and water. When we wash the surfaces, when we wash our hands with soap and water, when we wash surfaces with soap and water that fatty envelope is washed away and it causes the virus to fall apart. So, we are fortunate that the Corona Virus does have a fatty envelope, viral envelope because some viruses like the Norovirus have a different kind of envelope and they are much harder to disinfect.

Covid-19 is transmitted from person to person by contact, and from coughing that produces aerosols in the air that can land on you or surfaces and the aerosols carry the virus. That’s why it’s recommended that we stand at least six feet apart from each other and avoid touching surfaces or our face because once we get the virus on our hands and all of us touch our face. I touch my face about 20 times an hour then what we are doing is that transferring that to our mouth, our eyes, our skin and that’s going to make us more susceptible to being infected.

So, question number two is how long does the virus persist on surfaces?

Table 1: Persistence of Coronaviruses on Materials

Table 1: Persistence of Coronaviruses on Materials

The Covid-19 virus can live varying lengths of time on different types of materials. There is lots of information that’s been floating around out there on Facebook and other news sources and most of that is actually based on an excellent article that was published March 2020 in the Journal of Hospital Infection. And so that’s one of the best sources of information that we have.

I am going to show you a chart of some of the lengths of time that the virus can live on surfaces. Living is a little bit of a misnomer but it persists on surfaces. The virus needs to infect a cell in order to live. So the virus goes into a cell, it infects the cell, it reproduces in the cell and then it kills the cell and then spits itself back out. So, I am going to show you a list of the persistence of Corona Viruses on different materials.

So with metals the length of time is about 5 days, with wood the length of time is 4 days, paper can be 4 to 5 days, glass can be 4to 5 days. Those plastic bags that you zip-lock things into are made of poly propylene, the virus can actually live for 6-9 days on there. So ceramics can be 5 days, that’s sort of like we are for the sake of this discussion, we are classifying ceramics and brick together because brick hasn’t actually been tested and ceramics have. The last I have listed here is stone, there is a source available that’s online that says from 2-12 days but there is no research article to back that up so that’s why it has a double asterisk.

So, in general the longer persistence that we are looking at on surfaces is 6-9 days.

Now, another article has been published as a correspondence in the New England Journal of Medicine and this article gives shorter times for some surfaces. It says for example 4 hours on copper, 2 days on stainless steel, and up to 3 days on other surfaces. The difference between the New England Journal of medicine article is that it’s a communication and hasn’t gone through as thorough a review process as the article for the journal of hospital infection. So, in order to air on the sign of caution, I recommend that you isolate materials for 6 to 9 days.

So, how do we disinfect the virus?

Well, in the same article from the journal of hospital infection they looked at different types of disinfectants, their concentration and the length of time it took to destroy the virus on the surface.  So I am going to show you just a couple of them that are sort of important to our discussion.

So we are going to look at this one.

Table 2: Cleaners and Disinfectants

Table 2: Cleaners and Disinfectants

We can talk about ethanol at 95% strength and at 70% strength. We can talk about 2-propanol, which is often the rubbing alcohol that you get in your hardware store or your pharmacy and that we can look at 95% concentration and 70% concentration. Then there is bleach, bleach that you get in the store usually comes in about 10% concentration so what they are doing is really making a dilute bleach solution and then there is also Hydrogen peroxide. You can see that, you could use Hydrogen peroxide it takes about a minute to kill or disable the virus whereas with rubbing alcohol and some of these others it’s much shorter.

So, with these materials we can see that different surfaces would require different lengths of time and different disinfectants.

The CDC has made some recommends that are for general home use. What they say is that, if a surface is dirty you should wash it and clean it with gentle soap and water prior to disinfection.

Then you should use household bleach solutions, alcohol solutions with 70% alcohol or commonly registered, EPA registered household disinfectants. So this is for general home use.

The recommendations of the CDC. 70% Ethanol, 70% 2-Propanol which again is rubbing alcohol or a bleach solution that’s diluted to about 2%.

Table 3: CDC Recommends for General Home Use

Table 3: CDC Recommends for General Home Use

Okay, So.

Thus far we have been talking about the recommendations that come from the world health organization and the CDC. But that does not always apply to historic materials.

Why is that? Well, as conservators and conservation scientists we know that we must DO NO HARM to materials. We are the stewards of cultural resources left to us and we want them to be here for future generations. This includes things like your grandmother’s quilt, the family bible you might be reading, the historic house furnishings, the historic courthouse information desk, or even the original copy of the will that you need to take for probate court. It’s up to us to do the right thing.

So first of all, there is a choice between isolation and disinfection.

As human beings, we have the urge to fix things. I don’t know about you but I always want to fix things. We are quick to act but in emergencies sometimes, it’s better to slow down and assess the situation. In hospitals, that’s called triage. So, what is it that we really need to do first?

If at all possible, isolate the resource from people for a period of time. That means closing the gallery, bagging objects individually, leaving the building for 9 days. So you say that Why?

Well, that’s because historical materials can be irreversibly damaged, by some cleaners. If you must clean, if you have to remain open, if you have to use objects, then you are going to have to choose wisely.

Isolation is preferred method to deal with museum objects and collections. It will cause the least potential damage to the resources and provide a safe environment for the public once an appropriate length of time has passed. We recommend the isolation of a building, a site, or a collection for a minimum of 9 days based on our literature review. Some would say 3 but we think that the caution is the way we need to go here.

Isolation can also be undertaken at an object level. You can take zipper style plastic bags, the quart size, the gallon size, the two gallon size, the five gallon size. You can put your small objects into a zipper style plastic bag, double bag them, label with the object information, the date you have bagged it and why you have bagged it. Has somebody come through the visitor center, the museum, the court house that might be ill and have touched the objects? Since the virus can live on plastic bags up to 9 days, the items must be isolated at least that long.

What about when does cleaning and disinfection come in?

If isolation is absolutely not an option. Then again, you need to proceed with caution.

Do not undertake large scale disinfecting actions of the entire collections, or entire museum spaces without knowing the potential impacts to museum objects. For example, it has been suggested that one could use a wet fog of a biocidal solution which is based on a quaternary ammonium compound. This is not way to go with a museum collection. Many of those materials and they will interact differently with the biocidal solution. And you do not know how much you are applying with a fog. So, don’t try that.

Secondly, do not use bleach on these surfaces. Many cultural materials are sensitive to bleach. Bleach is a sodium hydrochloride it oxidizes to a sodium salt materials like stone, porous materials – brick, ceramics are all going to be damaged by bleach and bleach surfaces. Delicate finishes on wood would be affected long term by bleach and bleach surfaces.

So, if we are going to clean and disinfect then we want to start with painted surfaces, door knobs, and hand rails. You want to note if they are metal or wood and if they have any unique finish.

Next you are going to make up a soap and water solution from a mild or gentle soap. Soap has a polar end and a non-polar end. And so it tends to pull things into solution. The mild soap that we would recommend would be something like Ivory liquid soap or Orvus. But I would not recommend all dish soaps because dish soaps have other additives in them that can leave a film. I don’t know if you’ve ever washed your glasses with dish soaps, I actually have and it’s hard to get that film off and you don’t want to leave any film on your objects.

Once you have mixed up the solution, you place it in a spray bottle. You take a paper towel, wet the paper towel with your solution and then wipe the surface or the railing.

Now remember, back when we looked at those things, looked at the disinfection, it is going to take a little while, so you might want to wipe it down, come back and wipe it again in a minute. Once you have wiped the surface you want to dispose of that paper towel. That’s why you don’t want to use cotton cloths or other cloths you want to get rid of that paper towel.

You want to limit the amount of water or wet cleaning that you use since it can damage fragile historic materials like wallpapers or painted wall finishes. Again, after you wipe down the surface, dispose of the paper towel.

We are going to treat brick surfaces like ceramics and they can be wiped down with soap and water and then disinfected with an Isopropyl alcohol or rubbing alcohol solution that is at least 70% rubbing alcohol.

Rubbing alcohol can be used on some surfaces like marble, limestone, or terrazzo countertops or floors and this might be good use in government buildings.

Do not use rubbing alcohol on wood, since it can damage the finishes.

Pay attention to finishes. And if you have questions, you can reach out to us or find a conservator or conservation scientist through the American Institute of Conservation’s website and that is

Now, I want to talk a little bit about a note on U.V., that Ultra Violet light. While, the data is very clear that you can kill and inactivate viruses with U.V. germicidal radiation. That’s radiation at a specific frequency 264 nanometer or 365 nanometer of wavelength. We have not been able to find a reliable research article that recommends U.V. for Covid-19. U.V. can damage photographs and paper under long exposures. Now, we’ll keep you updated. What I want to know if I am going to use U.V. is what light do I need, how much light do I need and what power of light do I need and how much time? And I haven’t been able to find those sources to give you that kind of information.

The last question that I want us to talk about a little bit is my list for recommended for historic materials.

Table 4: For Preservation Use

Table 4: For Preservation Use

So for preservation use, we recommend first and foremost isolation for 9 days. If you absolutely can’t isolate it, use a a soap and  water solution to clean. And then you may also be able to use rubbing alcohol, 2-propanol, isopropyl alcohol those are all the same names for the same thing at a 70% solution. But be careful to sensitive finishes.

So, those are the things we want you to know about and we hope that works.

What safety precautions do you need to take when you are going be cleaning surfaces and disinfecting surfaces?

First and foremost wear disposable gloves when cleaning and disinfecting surfaces. The best gloves are Nitrile gloves, they are blue. Gloves should be discarded after each cleaning. Now they might be difficult to find right now, because they are being used in hospitals and you need to know that when we are prioritizing people’s lives are more important than cultural heritage. We are on the second tier here guys, I just hate to put it that way but we are.

So when the time is right get your gloves, and wear your gloves and dispose them after each cleaning.

Other personal protective equipment to consider would be goggles or safety glasses if you have them. Your regular glasses they are not enough, you need something that will fit to your face.

If you are responsible for cleaning a National Park visitor’s center, a museum collection, a government services administration building, you probably going to have to enlist contractors to help you. You’ll need to give them outer protective clothing, goggles or safety shields, surgical gloves, and if possible an N95 filter mask.

So that’s the information that I have for you today. As I say this will be recorded, we will also have our slides available on our website,

I need to thank some people who really helped me to pull this information together. First and foremost our research associate Vrinda Jariwala did a lot of work on this. Information came from National Park Service – from Brynn Bender and Margaret Brueker. And we want to thank the microbiologist emeritus Ralph Mitchell who is at the Harvard university.

So I hope that this gives you some basics that are worth beginning to look at and think about. If you have questions don’t hesitate to put them in the comments here. And we hope that this will be helpful to you.


  1. Kampf, D. Todt, S. Pfaender, and E. Steinmann. “Persistence of coronaviruses on inanimate surfaces and their inactivation with biocidal agents,” Journal of Hospital Infection 104 (2020) 246-251. Accessed March 20, 2020.

Brynn Bender, Northeast Museum Services Center, and Margaret Brueker, National Park Service, Historic Architecture, Engineering and Conservation Center, “Cleaning Protocols for Museums and Historic Sites,” personal communication, March 20, 2020.

Centers for Disease Control and Prevention, “Interim Recommendations for US Households with Suspected/Confirmed Coronavirus Disease 2019,”, Accessed March 22, 2020.

Neeltje van Doremalen, Dylan H. Morris, Myndi G. Holbrook, et. al., Letter to the Editor, “Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1,” The New England Journal of Medicine. March 17, 2020. DOI: 10.1056/NEJMc2004973

“How long can the new coronavirus last on Stone surfaces and how do you properly,” The Stone and Tile Radio Show and Podcast,, Accessed March 22, 2020.


  1. I should have mentioned that after you wipe down a surface with soap and water on a paper towel, you want to take a second damp paper towel and rinse with water.
  2. I want to emphasize that you don’t want to wipe down individual object without guidances. Isolate them. Seek professional advice.
  3. I am recommending no cleaning of museum artifacts in exhibit cases or in museum storage. The objects on exhibit are already protected by the case (just skip a month of housekeeping inside cases if that was scheduled). The objects in storage can be isolated individually for 9 days (double bagged) or keep the whole room closed for 9 days.
  4. If objects are in storage areas I would suggest (if possible) limiting access to only one person (consistently the same person) at this time to avoid cross-contamination. This person should use the CDC recommended hand-washing protocols and wear nitrile gloves.  If for some reason they need to clean in storage spaces (floors or cabinet exteriors) as per usual no solvent based cleaners – soap (Oruvs or Liquid Ivory) and water only – with limited water and rinsing. Cleaning would ONLY come into play for historic surfaces such as door knobs or handrails. Even with this as you said use extreme caution.

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