Ok, you're asking for the explosive for the letter...here's my recipe...Benzoyl Peroxide (cream at eBay ) on a little cotton ball with Methyl Ethyl Ketone (eBay) or anywhere ...you will get Kinepak explosive...use 4ml of emulsion...

https://www.ebay.com/p/Perrigo-Benzoyl-Peroxide-Acne-Wash-10-5oz-Bottle/1220304589?iid=272397781473

https://www.ebay.co.uk/itm/5L-Methyl-Ethyl-Ketone-99-7-ACS-MEK-2-Butanone-/130776166419