ABSTRAK.Penelitian ini bertujuan untuk mengetahui proses pembuatan sabun padat susu kambing dengan penambahan konsentrasi ekstrak kulit kopi cascara berbeda terhadap nilai pH, tinggi busa, stabilitas busa dan uji iritasi. Proses pembuatan sabun padat susu kambing menggunakan metode proses dingin (cold proces) dan diperam selama 4 minggu. Metode yang digunakan dalam penelitian ini adalah Rancangan Acak Lengkap (RAL) dengan 4 perlakuan dan 4 ulangan. Hasil penelitian yang diperoleh lalu dianalisis menggunakan Analysis of Variance (ANOVA) dan jika terdapat perbedan nyata maka dilanjutkan dengan Uji Duncan Multiple Range Test (DMRT). Perlakuan penelitian terdiri atas P0 (ekstrak kulit kopi cascara 0%); P1 (ekstrak kulit kopi cascara 3%); P2 (ekstrak kulit kopi cascara 6%); dan P3 (ekstrak kulit kopi cascara 9%). Hasil penelitian menunjukkan bahwa penambahan ekstrak kulit kopi cascara berpengaruh nyata (P<0,05) terhadap nilai pH, tinggi busa, stabilitas busa dan uji iritasi. Kesimpulan penelitian ini yaitu perlakuan P3 dengan konsentrasi penambahan ekstrak kulit kopi cascara 9% memiliki nilai pH 10,29, tinggi busa 8,49 cm, stabilitas busa 88,53% dan tidak menimbulkan adanya iritasi seperti kulit kemerahan, kulit gatal, dan kulit kasar pada panelis.Kata kunci: Susu kambing, sabun padat, ekstrak kulit kopi cascara ABSTRACT. The objective of this research is to investigate the production process of solid goat milk soap by incorporating varying concentrations of coffee cascara extract and assessing its effects on pH value, foam height, foam stability, and irritation test. The production of solid goat milk soap was carried out utilizing the cold process method, followed by a 4-week curing period. The experimental design employed in this research was a Completely Randomized Design (CRD) consisting of 4 treatments and 4 replications. The obtained research results were analyzed using Analysis of Variance (ANOVA), and if significant differences were found, they were further examined using the Duncan Multiple Range Test (DMRT). The research treatments consisted of P0 (0% coffee cascara extract), P1 (3% coffee cascara extract), P2 (6% coffee cascara extract), and P3 (9% coffee cascara extract). The research results indicate that the addition of coffee cascara extract significantly affects (P<0.05) the pH value, foam height, foam stability, and irritation test. The conclusion of this research is that P3 treatment with the addition of a 9% concentration of cascara coffee skin extract has a pH value of 10.29, foam height of 8.487 cm, foam stability of 88.530%, and no signs of irritation such as redness, itching, or roughness observed on the panelists' skin.