Colour changing fairy light painting

My 4 year old asked to do 'some science' so I quickly rustled up something with a Christmas theme.  I drew some wavy lines with a black permanent pen and added some blobs of two food colourings to look like fairy lights.  The food dyes I used are Tesco own brand in the UK, but the important thing to look for if you want to try it is the ingredients - the yellow is made from curcumin (found in turmeric) and the red colour comes from anthocyanins.  Both change colour depending on pH.  

I made my son a solution of bicarbonate of soda by dissolving a little in warm water.  I then suggested he try painting the 'lights' to make them change colour, like some of the lights he's seen flashing when we've walked past houses nearby in recent evenings.  Whilst the lights either use bi-colour LEDs or are actually several different colours of light but flashing in sequence, the idea here was to change the colour of the blobs!

Yellow and red fairy lights

The yellow curcumin changes to red when you add an alkaline solution, and the red anthocyanins (also found in red cabbage) change to blue.  My son was more excited by this than I was anticipating, given that he's done several colour changing activities before!  

Colour changes in action

He had fun completely changing the colours by covering the whole 'bulb' with bicarb solution, and painting patterns on the 'bulbs'.  In fact, he appeared to be having so much fun that his little brother who had spent the last few hours largely grumbling about any suggestions for things he might want to do was keen to have a go. 

After bicarb painting

I quickly set up a smaller version for the little one (who is almost 2) and he set to work painting.  He tried the white paper first and looked disappointed.  Then he painted a yellow blob and he was super excited to see it change colour.  

The little one tried his own

The little one changed the colour of all the blobs on his page, but wanted to keep painting them apparently in the hope of seeing another colour change!  I will have to try some of the colour change activities my eldest has done before with him as he's clearly old enough to appreciate them now, even if not to understand the science behind it!