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.

2

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)

7

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!!).

 

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One thought on “Breathing new life into a solvent dispenser

  1. Hi
    Really interestong post and really useful in the lab. Just to let you know that it is possible to buy the dispensers cheaply for under two pounds on ebay in different sizes.

    Like

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