How To Seal Candle Molds

By Bob Sherman

This article was originally published in December 2000 and has been reformatted and modernized for publication here.

Leaking Molds! This seems to be the bane of many beginners to the candle making hobby. I say beginners, because most experienced candle makers understand that a percentage of sealed molds will leak no matter what they do. There are some things that you can do to reduce the chances of a mold leaking, and that is what this article is all about.

PLEASE NOTE!! - Candle making can be dangerous if proper safety procedures are not followed. Please read these Safety Rules before attempting any candle making projects.

This article assumes basic candle making skills. If you are new to candle making, my Introduction To Candle Making Online Course is free and will show you all the basics for working with wax safely.

Why Do Molds Leak
Obviously, there are one or more holes in the bottom of an otherwise solid container. Assuming that aside from these holes, the mold is water tight (wax tight?), then these holes represent the challenge - they must be closed in a watertight manner. That is simplicity itself, just plug the holes! But wait a moment, what about the wick? Here is where it gets difficult.

• Wick is bi-directional. To put it simply, that means it will wick any liquid in either direction. You can probably see where this is leading - it is capable of wicking the liquid wax out of the mold, or if in a water bath, wick water into the mold.
• Any form of sealer needs a good mechanical seal. Putty must adhere tight, plugs must be a snug fit.

Mold Sealers
There are three primary types of candle mold sealer - putty, plugs, and magnetic.

• Mold Putty - This is pretty much the type of sealer most candle makers start with and many stay with it. Mold sealer putty is a highly adhesive, flexible substance. If used correctly the number of leaking molds is minimal.
• Mold Plugs - These are used more commonly in production shops because molds can be prepared much faster with plugs than with putty. Mold plugs are conical rubber pieces that are inserted into the wick holes. Although faster to set up, plugs will leak more often than putty. Furthermore, they are difficult to use with large wick sizes (the wick takes up more of the wick hole).
• Magnetic - Magnetic sealers are sheet magnets that work very well - if your mold is a magnetic material. These are great for standard metal molds, but useless on plastic or aluminum.

Procedure - Putty Type Sealer
The following procedure is the optimum way to use mold sealer putty.

1. The bottom (outside) of the mold must be clean. I don't mean a quick wipe, I mean clean enough to eat off. This is the number one cause of sealer failure. I recommend using a mold cleaner or wax remover. Even the slightest bit of dirt or oil may cause sealer failure. Even more insidious is the slightest film or bit of wax. The sealer will bond to it, but when the hot wax enters the mold, it will melt and separate from the mold causing the seal to fail.
2. Thread wick through the wick hole.
3. Attach wick to the wick bar. If using a quick attach bar that does not require a knot this may be done after step 8.
4. Pull the wick through the wick hole until snug and cut to 1 inch. Note: some folks prefer to use wick screws at this point, but I don't.
5. Coil the wick in a spiral.
6. Cover with a small piece of masking tape (this prevents the putty from staining the wick).
7. Knead a piece of putty into a disc larger than the masking tape.
8. Press the putty in place. it is essential that the wick and masking tape be completely covered, and a good seal made directly to the mold surface.
9. The mold is now ready for use.

Procedure - Mold Plugs
The following procedure is the optimum way to use mold plugs.

1. One of the time saving things about plugs is that the bottom (outside) of the mold need not be clean. Just make sure the wick hole is fairly free from bits of wax.
2. Thread the wick through the wick hole.
3. Attach wick to the wick bar. If using a quick attach bar that does not require a knot this may be done after step 5.
4. Pull the wick through the wick hole until snug.
5. While holding the wick taught, press the plug into the hole.
6. The mold is now ready for use.

Procedure - Magnetic Mold Sealers
Again, this only works with molds that will attract the magnet.

1. Make sure both the bottom of the mold and the magnetic sealer are clean.
2. Thread the wick through the wick hole.
3. Attach the wick to the wick bar. If using a quick attach bar that does not require a knot this may be done after step 5.
4. Pull the wick taught.
5. Cut the wick to approximately one inch.
6. Curl the wick into a spiral and hold it in place with masking tape.
7. Position the magnetic sealer.
8. Check to make sure the magnet is tight to the metal around the edges.
9. The mold is now ready for use.

Summary
As mentioned in the opening paragraph, some percentage of molds will leak and this is pretty much unavoidable. The three techniques have their tradeoffs. Putty and magnetic sealers are more reliable, but more time consuming to use. Plugs are much faster, but more prone to leakage. One thing I always do and highly recommend doing is placing the mold in a pan before pouring. This will contain leaks, reducing mess and simplifying wax recovery.

Candle Making Supplies

The following candle mold sealers were used in this article. Clicking on the item name will bring you to that item's page with a full description and ordering information.

Mold Sealer Putty

Mold Plugs

Magnetic Mold Sealer

Disclaimer: The information presented here is accurate to the best of my knowledge and common candle making practices as of the time of this writing - January 2008. This article originally published December 22, 2000 and has been updated and reformatted for re publication here. The author and the publisher accept no liability for the use or misuse of any of the information presented in this article. This article is presented for informational purposes and is used at your own risk.

Author: Bob Sherman

Publisher: Bobby's Craft Boutique Inc.

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