-note about heatsink

README.md

@@ -31,7 +31,7 @@ Turns a Raspberry Pi into a cheap, web-enabled kiln controller.
 | ![Image](https://github.com/jbruce12000/kiln-controller/blob/master/public/assets/images/max31855.png) | [MAX 31855](https://www.adafruit.com/product/269) | Thermocouple breakout board |
 | ![Image](https://github.com/jbruce12000/kiln-controller/blob/master/public/assets/images/k-type-thermocouple.png) | [K-Type Thermocouple](https://www.auberins.com/index.php?main_page=product_info&cPath=20_3&products_id=39) | Invest in a heavy duty, ceramic, k-type thermocouple designed for kilns |
 | ![Image](https://github.com/jbruce12000/kiln-controller/blob/master/public/assets/images/breadboard.png) | Breadboard | breadboard, ribbon cable, connector for pi's gpio pins & connecting wires |
-| ![Image](https://github.com/jbruce12000/kiln-controller/blob/master/public/assets/images/ssr.png) | Solid State Relay | zero crossing, make sure it can handle the max current of your kiln. You only need one SSR, even if the kiln is 220V. |
+| ![Image](https://github.com/jbruce12000/kiln-controller/blob/master/public/assets/images/ssr.png) | Solid State Relay | Zero crossing, make sure it can handle the max current of your kiln. You only need one SSR, even if the kiln is 220V. Relays this big always require a heat sink. |
 | ![Image](https://github.com/jbruce12000/kiln-controller/blob/master/public/assets/images/ks-1018.png) | Electric Kiln | There are many old electric kilns on the market that don't have digital controls. You can pick one up on the used market cheaply.  This controller will work with 120V or 240V (pick a proper SSR). My kiln is a Skutt KS-1018 |
 
 ### Schematic