This is a classic and simple lesson illustrating in a hands-on and clear way one mechanism for the recycling of paper products.
- Used paper
I have adapted the mechanism by proposing three methods of dispersing the cellulose fibers in the water. In proposing the beverage frothing tool (some of which operate with sound waves – an interesting variation on providing mechanical energy to break down the structure of the paper), I am hoping to avoid the potential for electrical hazard posed by powering a blender with an extension cord. I have seen this done quite often at science fairs and Earth day celebrations in gymnasia and outdoors, yet I tend to prefer the battery operated tools, particularly if you are running this activity with small children or in an open pedestrian space (there is an obvious potential for electrical hazard. If you elect to run this activity in an open area, use extra wide masking tape to secure the cable powering the blender if you are working on a wood or ceramic floor, and extra wide red, orange or yellow duct tape on an asphalt surface, such as a school parking area or paved playground). Please also observe all standard safety precautions, here specifically tying back long hair, rolling back sleeves, and ensuring that fingers stay away from the mixing of the cellulose fibers (younger students will want to touch the gray slur mixture, yet should be allowed to do so only after the blender is removed and unplugged).
Are you going to eat that?
Regarding the chemistry involved here, cellulose is an interesting compound to discuss with children. We eat it every day, yet lack the enzymes to break the bonds holding this molecule together. Children may know from health and nutrition lessons that dietary cellulose passes through our bodies undigested, yet they may be interested to learn that cellulose gel is quite commonly added as a thickening agent to processed foods to make them feel and taste “richer” and “creamier”. Typically it takes the form of microcrystalline powder that is added to low fat and fat free foods to add viscosity and a heavier “mouth feel” to processed dairy foods , including some forms of ice cream and non-dairy “shakes” served as fast food.
More commonly, plant based cellulose fibers, passing through our bodies undigested, help speed the passage of wastes through our digestive tract and are an important yet non-nutritive ingredient in our diet. Students may believe, inaccurately, that grasshoppers possess the ability to break down cellulose, yet in fact they depend on microorganisms in their digestive tract who do the work for them, in exchange for “housing” and board inside the grasshopper’s body. The arrangement, in science, is called symbiosis., as both parties benefit from it.
Here we have perhaps the cheapest, most commonly accessible cellulose fibers in the form of newsprint, which itself is typically considered “post-consumer” material in that much of it has been recycled once already. Depending on where you are viewing this segment, the inks used in the newsprint are likely based on soy compounds, yet you should still ensure that your students wash their hands with warm, soapy water after any science experiment. I would hope that every science classroom has a bin of newspaper at hand because it’s so useful in so many lessons. We plan to feature it prominently in several upcoming segments, so begin your stockpile by asking student volunteers to collect unwanted newsprint from the school library or office (try to get there before the art teachers).
Avoid a Sticky Situation
I have elected to “re-adapt” the use of the mesh in the kitchen strainer because it’s a high quality (food grade) stainless steel mesh. Because of the thickness of the wire, I’m able to “form” the mesh into a workable shape. It also does not curl and buckle under the weight of the slur (the water and cellulose mixture). You may elect to use window screens (ideally salvaged from scrap material), yet be aware that particulates on the screen material may adhere to the recycled paper as it dries onto the screen form. For this reason, pack a Teflon or thin metal spatula to help “dislodge” the paper from the screen. I have seen students and teachers frustrated by recycled paper that can not be removed from the screen surface without fraying and becoming damaged, and I want you to avoid that situation. The chromium content of the food grade stainless steel in our version of this experiment allowed us to easily dislodge the final product with a large pair of forceps purchased from a science surplus company.
We propose adding the shavings of colored pencil sharpenings to create a “marbling effect” on your final product. Add small amounts at first to avoid producing a textured product that is too brittle because of the addition of the wood shavings (they, too, are composed of cellulose and quite commonly recycled – or post-consumer- content made from scrap lumber). Observant students may comment that the more expensive colored pencils are actually water soluble. In this case, you will notice a slight tinting effect in your final product as the pencil tips dissolve in the warm water. Students have also added various other materials to the mixture, including feathers and “confetti” harvested from the paper puncher. In these instances, the final form is more an art project than workable paper source. In our segment, we were able to trim the final product into a card shape and label it “Science House” because it was smooth and pliable enough to trim and write on. A drop or two of chlorine bleach can lighten the final product, yet ensure that it is dissolved into the water before hand so that the students are never in the presence of concentrated bleach (the chlorine atoms in the bleach belong to the halogen family and, as such, are quite powerful oxidizing agents that can damage clothing and irritate skin).
Timing is everything…
Off camera, we have in fact dried our sample in an oven with temperature set on “warm” and observing the sample constantly until removing it. We were able to do so here because our mesh is composed of stainless steel. Yet if you work with window screening, avoid warming it in the oven because many forms of it are composed of polymers that can melt or contract when heated, and some contain Teflon, a fluorine containing compound that can become unstable when heated. Here again, we recommend using the food grade stainless steel from a kitchen strainer, and purchasing one second hand for this purpose as we have. If you teach earth science, you may in fact have a series of screens that are used to strain silt from a river bed. These are ideal for this purpose, yet are often round in shape, so your final product may require trimming as ours has. We recommend drying all samples prepared in schools in sunlight because it’s safer and “greener”. Also, we’d like to remind you to avoid leaving the gray slur (the water and cellulose finder mixture) untended for more than a few hours because it mold colonies typically form on the surface of the slur within a day. Unless you’re studying slimes and molds, we encourage you to quickly process the slur into the paper form as we have.
If you elect to try paper recycling with your students for the first time, share your experience with me on our Science House Blog. We’d enjoy hearing about your experience.
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