Elderberry pH change art

We've used lots of different natural pH indicators in previous activities, including red cabbage, blueberries, blackberries and turmeric, but we found another one this week.  I spotted some ripe elderberries when we were out on a walk, and picked a bunch to bring home and try out - I thought they were likely to get their deep purple colour from pH-sensitive anthocyanin pigments and this turned out to be true.

My boys both enjoy hitting things (occasionally each other...) with a toy hammer, and I thought it'd be fun to try squashing the elderberries between two sheets of paper to colour them with the juice.  My 3 year old had a whale of a time, although he also decided that it was more fun to just hammer them directly onto a single sheet of paper, which leads to more juice squirting around and more mess on clothes.  In fact, the first confirmation I had that the colour was pH-sensitive was when putting stain remover (which is alkaline) on the stains on his shorts immediately afterwards, before the juice had dried!

Squashing elderberry

I dried the squashed berries overnight, and in fact we left them for a further day before experimenting.  I tried to make it so that both boys could try it out - my younger son is 1.5 years old and likes to join in with everything his brother is doing.  I put one of the sheets of paper with squashed elderberries out on a plastic tray for each child, and gave them a piece of cotton wool dipped in vinegar, and one dipped in bicarbonate of soda dissolved in water.  The vinegar is acidic and the bicarb solution is alkaline. 

Changing the colour of squashed elderberries

I asked them to use the cotton wool balls to draw on the elderberry stains, and see whether they changed the colour.  My 3 year old wanted to know what was on them, so I told him and I asked him to predict the colour change - he was correct, the acid turned the purple stains a bright pink and the alkali made the purple a darker blue.  He made a pattern of blobs on one sheet of paper, and on the second one (he made more than I anticipated when he got a bit carried away with the hammering...) he asked me to draw an upper case and lower case E (for elderberry!) for him to trace over with the cotton balls, then he used the vinegar for the upper case and bicarb for the lower case E.

Upper and lowercase E

The little one was curious about it, and although he's generally into mark-making and mess, he wasn't keen on the idea of using the cotton wool balls to make marks.  Maybe because they were white and they changed the colour in ways that he didn't understand, or because they smelt strange, I don't know.  He was fascinated to see what happened when I did it or his brother helped, but definitely didn't want to try himself!

Mark-making with vinegar and bicarb

The berry smashing aspect of this activity was definitely the best bit for my 3 year old, but the younger one was definitely curious about the apparent magic of something colourless changing the colour of the paper it touched.  It was a nice simple way to do this activity with very little preparation needed, and I was pleased to find another natural pH indicator that we can use in future.


Post a Comment

All comments are moderated before being published.