Insecticidal soap

I have an aphid problem on my overwintering/indoor plants, and I think a soap spray solution would do the trick. I make cold-process solid soaps, and could easily make one with neem oil for the plants- however the spray solution will obviously have to be liquid. Can I dissolve solid soap in water to make insecticidal soap, or should I make actual liquid soap? (so use potassium hydroxide rather than sodium hydroxide)

If I'm making my own soap then Wikipedia suggests insecticidal soap works best with long-chain fatty acids (https://en.wikipedia.org/wiki/Insecticidal_soap), so olive oil, castor oil and sunflower oil base.

Also, any preferred recipes or inclusions for aphid deterrence? Or other bugs/critters?

Soap kills insects by drowning them as it changes the surface tension . Surface tension being the process whereby water forms drops ; If you reduce the surface tension of the water the water can enter the breathing holes of the insects and "drown "them so you do not need that much soap usually I use one drop per litre . Using too much actually can make the liquid less effective ;
I think your liquid home made soap would do fine no need for extra sodium hydroxide .

david  

I've never actually made liquid soap before- only the solid variety. I'm sure I can make liquid soap though, different chemical and different quantities of oils, but it isn't a vastly different process.

I didn't think that solid soap dissolved in liquid was anything like the same as actual liquid soap! But various internet sites (like this one: http://www.hpaa.org.uk/index.php/controling-pests-diseases/256-insecticidal-soap) just say to dissolve solid soap.

Charli Wilson wrote:I have an aphid problem on my overwintering/indoor plants, and I think a soap spray solution would do the trick. I make cold-process solid soaps, and could easily make one with neem oil for the plants- however the spray solution will obviously have to be liquid. Can I dissolve solid soap in water to make insecticidal soap, or should I make actual liquid soap? (so use potassium hydroxide rather than sodium hydroxide)

If I'm making my own soap then Wikipedia suggests insecticidal soap works best with long-chain fatty acids (https://en.wikipedia.org/wiki/Insecticidal_soap), so olive oil, castor oil and sunflower oil base.

Also, any preferred recipes or inclusions for aphid deterrence? Or other bugs/critters?

If you have neem oil (or neem soap) dissolve it in hot water allow it to cool but still be warm (otherwise your sprayer could block in a cool environment) and then spray. The neem is effective enough on its own to kill aphids you wont need anything else if it is present in a resonable quantity.

I do this all the time with just neem oil so add some detergent to stop it clumping together too much. I also use a seperate sprayer for neem as it tend to stick around in the sprayer and you never should spray it on a plant in flower that a bee could gain access to.

You could buy critters to eat the aphids e.g lacewings, ladybirds but if its just for a few plants or you overwintering environment doesnt all they need to survive its not really worth the effort of buying them.