Material Spotlight: Agar Gel

Robert Price

I’m just going to come out and say it – gels are pretty amazing.

Jurassic Park (1993)

Jurassic Park (1993)

No, not this kind…

I mean, sure, Jell-O or Jelly is pretty great too, but I’m talking about the gels used in conservation and my new favorite gel – Agar.

If you’ve done some lab work you’ve probably come across Laponite RD (a synthetic clay), Carbopol (a carbomer resin), or Cellulose Ethers like Methyl Cellulose or Sodium Carboxymethyl Cellulose being converted to gels for cleaning techniques involving water, solvents, or other cleaning agents.

Gels are useful because they minimize the total amount of solvent or water needed for a treatment by slowing the rate of evaporation and maintaining good contact with the surfaces targeted for cleaning – this is good for you, the environment and the object. In some circumstances gels can also have a poulticing effect and are capable of absorbing a portion of the materials they solubilize or soften.

Aside from potential chemical interactions, a big consideration with gels is how easily you can remove them once they have worked their magic – a process known as ‘clearance’. With some gels this might be particularly problematic, especially when used on very rough or porous surfaces. Not all gels are the same though and you need to do some research.

But here’s where my new favorite material comes in – enter, Agar gel.

If you look into the literature you might be surprised to see the wide range of materials it has been used to clean, including: wax sculptures, marble, gypsum plaster, ceramics, wood, and textiles. Anecdotal reports from our peers currently undertaking work placements have also noted its growing use within museums, especially for surface cleaning on limestone.

The beauty of the gel is that it’s capable of slowly releasing water in very small amounts, which means that it can be used to remove or soften water-soluble materials without overly saturating a water sensitive surface. Unlike other commonly used gels, the rigid gel formed by Agar is extremely easy to remove in a single piece and leaves no visible residues behind. This minimizes the amount of mechanical action needed to clear the gel. You should be aware, however, that at least one study has identified trace amounts of polysaccharides within cleaned materials analyzed with GC-MS.

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Comparative clearance tests with commonly used gel concentrations on Melinex

Personally, I have found it to be a promising material for softening and removing proteinaceous glues in situations where excessive amounts of water or heat would be problematic for the object being treated – as is the case for bone and wood.

It’s definitely worth experimenting with, even if you don’t currently have a use for it. While purified agarose can be purchased online, food grade Agar is much cheaper and can be purchased from higher end grocery stores. Even some high profile cleaning projects have gone with this cheaper alternative. I’ve been using Clearspring® Agar Flakes.

Try making a 2% w/v gel by adding 2g of agar flakes to 100ml of boiling water and a allowing the solution to cool within a flat container. The resulting sheet can be cut into whatever shapes you need and will keep in the fridge for a week or more depending on the cleanliness of your equipment and how often you open the container.

A square of Agar gel, roughly 3mm thick.

A square of Agar gel, roughly 3mm thick.

Unfortunately, these tidy little sheets only work well on flat surfaces. As an alternative, the semi-cooled solution can also be placed in a plastic syringe and extruded just before gelation occurs, allowing the gel to better conform to complex surfaces. This takes some practice and familiarity with the material but can be very effective.

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Direct application of the gel near its ‘sol-gel’ transition temperature.

Finally, you can also experiment with forming the gel around other materials as I did with natural fiber strings. The string can be repeatedly dipped in and out of the warm solution until a thick coating is formed around the fibers. Strings with looser twists and greater surface area work best. This gives the gel a support structure and made handling and removal even easier. Possible applications could be for disassembling narrow joins or lying over curvilinear shapes.

Non-dyed, natural fiber strings used as ‘scaffolding’ for the gel

Non-dyed, natural fiber strings used as ‘scaffolding’ for the gel

Hopefully this has been helpful and got you excited about exploring Agar gel further. It might be a good alternative to consider the next time you have to remove proteinaceous glue from a fragile or water sensitive surface.

 

 

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Breathing new life into a solvent dispenser

Dae-Young Yoo

In our lab, we frequently hear “does anyone have extra acetone? IMS? White spirit?” Here, the solvents do not mean just solvents, it actually means a solvent dispenser filled with a specific solvent. Why is this such a frequent problem? Let’s find out the reason and sort it out!

Solvent dispensers have been used in conservation labs for some time. These are pump action bottles that allow the controlled use of solvents during lab work. There are many advantages to using these dispensers. Firstly, it makes the controlled application of solvent to cotton wool swabs or brushes much easier, without contaminating the rest of the solvent . The pump on the dispenser transfers a small amount of liquid to the cup at the top. Therefore, there is no need to worry about an excess of solvents or accidental spillage. There are health and safety advantages to using solvents in this way, as it reduces the evaporation rate of solvents, and reduces potential exposure to solvent fumes. Lastly, it is made of plastic which makes the dispenser shatterproof. Even if you drop the dispenser, it remain as it is without gushing solvents out of it.

A solvent dispenser can control the amount of solvent. It makes it easier to apply cotton wool or brush (photo courtesy of Dae Young Yoo)

These solvent dispensers are very useful for conservation practice and routinely used in the UCL Conservation lab. So when they go wrong it usually results in a frustrated cry for help. One major drawback of the solvent dispenser, is the durability of intake tube inside the dispenser bottle. I am not sure if this problem applies to all dispensers in the world. However, most dispensers I have used fail to function because of a problem with the tube, rather than other parts of the dispenser. Most of the broken dispensers in my lab have the same problem. So I figured out why so many classmates end up suffering while pushing the dispenser pump to no effect, and then ending up ’borrowing’ other classmates dispensers. It is really annoying that something does not work properly when necessary.

In this post, I will let you know how to fix it, with materials that are easily available in your lab or workplace. It is super easy and only takes three minutes to fix . I hope this post helps not only my classmates, but also conservators fix broken dispensers by themselves, and therefore remove one element of conservation lab stressing out.

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A crack on the tube reduces air pressure in the tube when the pump at the top is pressed. The principle of pump is the air pressure difference between inside and outside of a tube. Because of the crack, the air pressure between inside and outside of tube is the same, which makes it difficult to suck up solvent in a dispenser (photo courtesy of Dae-Young Yoo)

How to fix it

Everything you need:

– A disposable pipette made of low-density polyethylene (LDPE, which has resistance to acetone, ethanol, white spirit and IMS)

(Note: You should check what your disposable pipette is made of and what types of solvents will be used because some plastic pipette are easily dissolved in some solvents)

– A hot air blower, or a lighter in extreme situations where a hot air blower is not available

– scissors

  1. Heating a pipette

Heating a pipette with a hot air blower.  (photo courtesy of Emily Williams)

Ensuring you have first carried out a risk assessment, and have access to suitable Personal Protective Equipment and fume extraction, heat a disposable pipette with a hot air gun until the colour of pipette becomes transparent. Turn the pipette to ensure that the area is evenly heated. Do not heat just one spot, otherwise the pipette will be burn. In addition, before heating it, you have to consider the height of a dispenser and decide the location of the pipette for heating.

  1. Pulling a pipette
When the heat is applied, the pipette get transparent and soft (photo courtesy of Emily Williams)

Pulling a pipette while it is warm. When the heat is applied, the pipette gets transparent and soft (photo courtesy of Emily Williams)

The pipette is made of polyethylene, which is a thermoplastic polymer. The thermoplastic can be soft when heated and hard when cooled. We will take advantage of the properties of thermoplastic.

Pull the pipette from both sides considering the diameter of the solvent intake. You have to adjust the length of the pipette before it is cooled otherwise it will get hard in a short time so you cannot transform the pipette.

  1. Cutting a pipette with scissors
Separated pipette (photo courtesy of Dae-Young Yoo)

Separated pipette (photo courtesy of Dae-Young Yoo)

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Separated pipette (photo courtesy of Dae-Young Yoo)

  1. Replacing the broken tube with a new one
The pump with a new intake tube (photo courtesy of Dae-Young Yoo)

The pump with a new intake tube (photo courtesy of Dae-Young Yoo)

Replacing the tube is easier when the tube is warm. Otherwise the tube will get hard and could be difficult to fit it into the intake of the pump.

  1. Installing the new pump

(photo courtesy of Dae-Young Yoo)

Solvent dispensers with newly made tubes are working well in our lab. From now on, if you find a solvent dispenser broken, do not throw it away, and pinch another from your lab mates. Check the intake tube inside. If it is broken, just spend three minutes to fix it. Just three minutes will make the dispenser semi-permanent and save money (the price of solvent dispenser is usually over 10 pounds!!).

 

Conservation Tool Spotlight: Silicone Brushes

Madeline Hagerman

No, not like this one. (Image from Wikipedia).

No, not like this one. (Image from Wikipedia).

This past summer in the midst of writing our MA dissertations, we received a list of tools to purchase. As I perused the list, I felt a bit like Harry Potter, new to the wizarding world, reading his school list for the first time. While the list included familiar items from my oil painting days, such as a plastic spatula, it also specified the need for “Needle holder, with rustless chuck” and “Paint brushes (sable, squirrel and hog’s hair).”

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I may have been a little too enthusiastic in my purchasing of bamboo skewers.

I decided also to buy silicone brushes on the advice of a former MSc student. Silicone brushes, you may ask? Yes. Though not like the lovely pastry brush above.

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Voilà!

They come in different sizes as well. From tiny (Size 0, top), for detailed work, to more moderate sizes (Size 2, bottom) for general purposes.

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They have been especially helpful for work on my delicate porcelain teacup. I used my brush to apply Araldite 2020 (an epoxy resin) to the joins of the cup. This method of application utilized the tight nature of porcelain fractures to allow the epoxy to be drawn into the join through capillary action. I also used my silicone brushes to fill the small chips on the joins of the teacup.

Applying Araldite 2020 mixed with polyester pigments to fill a chip in the interior surface of the teacup.

Applying Araldite 2020 mixed with polyester pigments to fill a chip in the interior surface of the teacup.

The owner had specified she wanted the cup to be fully restored to its original appearance. As such, I infilled the gold paint around the rim. I used a silicone brush to make sure all of my lines were straight. They were well-suited to this task because they easily wiped the excess paint off of the surface of the teacup.

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Fellow conservation student Kristen Gillette also used silicone brushes to fill chips on her high-fired ceramic.

 

Making sure the inpainting lines are all straight.

Making sure the inpainting lines are all straight.

Silicone brushes are not only good for porcelain and other high-fired ceramics, but also especially useful for glass repair and restoration.

Abby Duckor, lab partner extraordinaire, uses HXTAL (another popular conservation epoxy resin) to rejoin a practice piece of broken glass.

Abby Duckor, lab partner extraordinaire, uses HXTAL (another popular conservation epoxy resin) to rejoin a practice piece of broken glass.

Silicone brushes have become a bit of a lab sensation. They are useful for the application of all manner of adhesives: epoxy resins and Paraloids a là the ubiquitous B-72, to name a few. In the restoration side of conservation, the brushes allow conservators to easily create small epoxy resin fills. Because they don’t stick to paint or most adhesives, they can be used to clean up inpainting from smooth surfaces, like glass and resin. Silicone brushes are definitely my favourite conservation tool!

*As a North American student in London, Harry Potter continues to provide many of my points of comparison for British life.