Colours and dyeing

Last term our little science club in Manly had some great activities exploring colours and dyeing.

We started off with a packet of synthetic dye and some squares of cotton. We left the fabric in the dye and used tongs to take out one piece every 5 minutes, until the last piece had been in the dye for one hour. We used the leftover dye to do some tie dyeing and put in some of my little girl’s clothes too.

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The square we removed after 60 mins looked lots darker than that for 5 mins but we did wonder if that was perhaps because it was wetter.

We left all the fabric squares for a week to dry out, then shook them up with warm detergent solution to see how much dye would actually stay fixed onto the fabric.

I was hoping that we would be able to see by eye how much dye had gone back into solution, but we couldn’t really tell. (Perhaps a spectrophotometer would have come in handy at this point, but we don’t have access to a lab and it’s rather outside the budget for our club!) However, the 5 min piece of fabric looked loads paler than the 60 min, so we could at least deduce that more dye molecules had attached themselves onto the fabric that had been in there for longest.

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The children and I thought about what we were trying to find out in this experiment. We discussed what is meant by the scientific method and the idea of a fair test. They were really good at suggesting what variables there might be in the experiment and how we could try to keep all of them constant except the one we were testing.

If doing this again, I would reduce the number of samples to six (as suggested in the instructions) and allocate more than one pair of disposable gloves per child, because they took them off in between turns. I had hoped it would be more obvious which fabric samples had been left in the dye solution for longest. Perhaps we could experiment with the concentration of dye solution to give more of a contrast.

This activity came from the booklet of ideas for the CREST award scheme (run by CSIRO). My two young scientists-in-the-making were not so keen on the technology activity (which personally I thought was predominantly design and very little to do with technology). I think this has been a good example of making sure the activities follow the children’s interests. Furthermore, it seems to me that successful inventions or designs come from perceiving a need or a gap in the market, rather than just doing an activity that someone else has set for you.  I’m not going to set them an activity we all think is pointless just so they can get a certificate. If the children decide that there is a design activity they want to do which revolves around the use of colour, I will encourage them in this.

Anyway, we were all very interested in natural dyes and the ochres that have been used for thousands of years by the Australian aborigines. I borrowed a selection of books from our library all about natural dyes and a few about design (and tried to stop myself from taking on more projects than I have time for). We boiled up some chopped red cabbage and water in one saucepan and some onion skins and water in the other. As it was the last week of term we didn’t have enough time to dye fabric (or yarns) and wait for it to dry. Instead, we used the natural dyes like watercolours. I made some strong tea and coffee for brown colours. Dickie Turpin painted a beautiful landscape but didn’t want me to take a photo of it!

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The same day, we ground up a rock we had picked up on a bush walk, mixed it with oil and used this to paint with. This was a lot easier than I had expected and produced some great results.

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The project has been very successful so far and still has plenty of potential. I would like to show the children the molecular structure of some dyes so that they can think about what the common features might be that contribute to the colour. We have done some subtractive colour mixing in our homeschooling before (with paint) but it would be fun to get some colour filters and show them how additive mixing works. This might or might not lead to a discussion about the electromagnetic spectrum, waves, frequency, wavelength etc. We could move on to talking about our eyes and how we see colours. (I have a particular interest in this because Pokemon Boy has some red-green colour deficiency. He’s fine with bright colours but finds it a lot harder with muted colours.)

We all want to do some more work with natural dyes and I must remember to order some alum to use as a mordant so we can see what difference that makes. (Mordants help the dye molecule to bind to yarn or fabric.) In the school holidays the children attended an activity (not run by me) where they used cabbage water as an indicator, so we could talk more about pH and indicator solutions. All of this is only if the children want to! I’m happy to be led by their interests.

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