Don’t think many people do this any more – make your own keropok (note my grandmother’s different spelling) from scratch. Normally, we’d just buy the dried, raw version in slices and deep fry it. Or more likely, we just buy keropok ready fried and sealed in nice plastic packaging.
As for ‘Robin Starch’, the strange thing is that my internet research indicates it was a household starch mainly used for starching clothes and bedlinen, not cooking! Then again, clothes can be starched with a variety of edible products such as cornflour/cornstarch + water, sugar water, rice water or potato water; but I’m not certain what the ingredients in Robin Starch were. Robin Starch was produced by Reckitt & Colman (Reckitt of ‘Reckitt’s Blue’ and Colman of Colman’s Mustard, which we can still buy today, merged in 1938). By the way, I love this postcard of a little cat looking at box of Robin Starch!

I’ve just updated this entry with a section on Robin Starch, based on my brief internet research.
What does juice of prawn shells mean?
i) Squeeze shelled prawn shells in a towel?
ii) Drip through a webbed tray onto a tray?
Thanks. :)
Sorry it’s taken me so long to reply but I had to track down one of my grandmother’s friends to ask!
What you do is: keep the shells and head of peeled prawns. Stiry-fry the shells/heads and liquid will emerge. This liquid is the ‘prawn juice’. Hence the instructions above for prawn juice ‘without water’. They’ll add a good prawn flavour to the keropok.