Ok so I'm making some hard alcohol from a sugar-wash. I used too little yeast and fermentation ended up halting at like 7% ABV, it then stood around for like a week and a half till I got the new yeast. I freeze distilled most of it after it finished, hopefully at around 13% but can't tell because I added some water with the new yeast, used a sterile syringe and distilled water. Because I used a new container and my calculations were waaaay off, I got something really sweet, so I'm using it as a base for alcoholic lemonade instead of the usual ultrasonic aged whisky I make. I drank like 2 glasses and I'm fine, but I drank them slowly in the evenings. It has a bit of a weird off-taste, but, to me at least, not bad, more fermenty, even though stronger then the one I get when I make kwass(didn't get time to turbo clean it yet though). My question is, is there any chance it has something harmful in it from just a sugar wash? Because with the halt and all the process took like a month, even though it was mostly hermetically sealed for that time. I'm a bit paranoid about getting drunk on it. Even after freeze distilling it's not strong enough to light on fire but if I heat like 100 ml of it and keep an open flame on top, I get like a second of yellow flame(methanol probably) then it goes out and start burning transparent or blue in the dark, I never let it go till the end cause it seems like it wanted to burn for a while. By the burn test the methanol content should not be an issue(I think). Any thoughts?
No, from brewing just with yeast, and even from a bit of freeze distilling, you won't get harmful chemicals in your beer. Also not from letting it stand before you added other yeast. It could get contaminated with other bacteria, yeasts or fungi, but at 7% alcohol at that point, I doubt if they would feel fine and ferment further.
The test with the flame does not mean anything. Ethanol and methanol burn the same. A yellow flame is just incomplete combustion. Once the alcohol is warm enough, you get a proper complete combustion, signified by a blueish flame.