---
title: Air dry and seal
slug: air-dry-and-seal
step: 5
howto: make-plaster-moulds-for-large-products
tags: ["product","injection","extrusion","mould"]
category: Moulds
difficulty: Medium
time: < 1 week
location: 
---
# Step 5: Air dry and seal
Once you have both parts of your mold, it is advisable to let them air dry for a couple of days. You will notice when they are touch dry (and significantly lighter), indicating readiness to proceed.

As an optional step, apply a layer of shellac on the plaster surfaces. Upon curing, you may then apply a mold release agent, such as silicone oil or petroleum jelly, to ensure that plastic does not adhere to your mold, allowing for repeated use.
![IMG_3599.jpg](/resources/howtos/make-plaster-moulds-for-large-products/img_3599.jpg)
![IMG_3548.jpg](/resources/howtos/make-plaster-moulds-for-large-products/img_3548.jpg)
![IMG_3654.jpg](/resources/howtos/make-plaster-moulds-for-large-products/img_3654.jpg)