Old-Fashioned Dishwashing Detergent 1 pint grated hard bar soap, soap ends or soap flakes 1 gallon water Place into a pot and stir. Heat over medium heat until it boils, stirring occasionally, until soap dissolves. Lower heat and simmer for 10 minutes, stirring occasionally. Remove from heat and let liquid partially cool. Pour into a clean container and cover tightly. Use about 1 teaspoon to a dishpan of hot water.