Container candles - Wax Formulas
There are probably as many container wax formulas out there as candlemakers!
The ideal formula must have multiple qualities that we will review now. Unless you'll be using a commercial blend, be prepared to spend a lot of time and do a lot of testing before you find the key to YOUR ideal wax formula...
As we already know, because of its chemical composition, paraffin expands when it gets heated and takes on a liquid form and contracts when it cools off and returns to a solid state.
This is definitely a good thing when you're working on pillar candles, for example, or other molded candles, because it makes unmolding the candle so easier.
But in the case of container candles, this expansion/contraction behaviour is really an inconvenience because the last thing you want is having the wax pull back from the sides of the container and ending up with a shrunken block of paraffin rattling inside your jar!
In this case, only one thing to do:
use any means to prevent the contraction of the wax during the cooling process.
To achieve this goal, there's only one solution:
make sure that the temperature at which you pour the wax into the container is as close as possible to the room temperature..
Let's examinate what our options are:
use a wax formula with the lowest possible melt point (MP)
Straight paraffin has an average melt point of 284°F. The difference between the melting temperature and room temperature is rather large and will probably trigger a strong contraction (think of the shrink well that appears when you make a pillar candle).
pour the wax in the container at the lowest temperature possible
Candle wax manufacturers offer a large range of waxes with different melt points for all sorts of applications (see for instance the pages about candlemaking waxes on the IGI Wax website) amongst which a range of specially formulated container waxes with a relatively low melt point (usually between 259°F and 268°F)
You see where I'm heading: wax with a MP of 259°F doesn't have to "come such a long way" when it returns to room temperature and will be less likely to develop a shrink well.
If you have access to a low melt point paraffin, use it instead of classic paraffin, it will give you a head start.
Logically, the hotter the temperature you pour at, the largest the difference with the room temperature and the strongest the contraction.
modify the chemical structure of the wax in such a way that it will shrink less when it cools
This golden rule applies to all container wax formulas:
let the wax cool off as much as possible before you pour..
When you watch paraffin cool off in a pouring jug (I know, I have exciting hobbies!), you can notice that when the wax reaches its congealing point (the temperature at whick it starts returning to a solid state), un thin skin starts to form at the surface, starting from the sides of the jug.
This is an indication that it won't take long before the wax returns to its solid state. And it is also the best time to pour the wax into the container.
A few important points, though:
With a little experience, you will learn to know when the time to pour has come without the help of a thermometer.
- at this temperature, the wax is thick and any air bubbles that may form when you pour won't be able (because of the viscosity of the wax) to reach the surface and burst. So try and pour as slowly and from as low as possible, tilting the container whenever possible (like you do when you pour a beer and want to avoid the formation of foam)
- the wax is almost cold. If the containeris cold as well, when the wax touches the inner walls of the container, it will solidify instantly and create what is called jump lines (light colored horizontal lines). It's actually a quite nice effect that can be intentionnally created by placing the container in the fridge during thirty minutes before pouring but if you want to avoid it, you should heat the container in a lukewarm oven during ten minutes before you pour (or, alternatively, heat it with a blow of your heatgun)
The good news is you don't need a particle accelerator or a master in molecular chemistry!
use a type of wax that does not dilate/contract, alone or mixed with paraffin wax
However, a teaspoon of chemistry is needed to understand how it all works:
As explained in the article about paraffin waxes, paraffin is made mostly of long-chain saturated hydrocarbons that don't interact with one another. When paraffin is heated, the molecules start vibrating because of the thermal energy, causing a dilatation. Following the same rule, when paraffin cools, this energy is lost and a contraction occurs (picture this: a row of people standing side by side, arms along their bodies, shoulder against shoulder. Hot, they extend their arms horizontally, sidewise and push each other away; cold, back to the initial position).
On the other side, vegetable oils are acids with a high molecular weight (fatty acids). They have carbon-carbon double-bonds as well as oxygen atoms that allow them to interact with one another thanks to an hydrogen bond. Because of this and in opposition to paraffin, these oils do not expand (or almost not) when heated.
Hydrogenated vegetable oils have some of their double-bonds saturated with hydrogen, which creates tristearines, hard and wax-like. To make a long story short, the more it's hydrogenated, the harder the consistency is.
As an example, soybean oil is not hydrogenated and is liquid. Vegetable shortening (Crisco) is partially hydrogenated and is a firmer semi-solid.
Hydrogenated vegetable oil (HVO) - for example, vegetable shortening - is chemically compatible with paraffin but does not expand when it is heated. So by mixing hydrogenated vegetable oil and paraffin, you get a wax formula that is less likely to dilate / contract than straight paraffin.
However, if the selected oil is not fully soluble in paraffin wax, the obtained candles run the risk of "bleeding" or "sweating" oil. In this case, you need to add a binding agent like Vybar™ or, to a lesser extent, stearic acid.
The dilatation/contraction behaviour is specific to paraffin but there are other waxes than paraffin waxes that do not have this dilatation drawback.
Another important property of a good container wax blend is its ability to "stick" to the sides of the container. To achieve this goal, always add a small proportion of soft microcristalline wax, which is a rather tacky wax, to your wax formula.
Beeswax, for example, has a chemical structure TOTALLY different than that of paraffin wax and won't budge when you heat it or when it cools.
In other words, a wax formula with equal parts of beeswax and paraffin wax will tend to shrink less during the cooling process, especially if my previous piece of advice (pouring temperature) is applied.
Another type of wax that won't dilate/contract (much) is soywax. It's getting more and more popular, even in Europe, and is becoming easier to find nowadays so don't hesitate to include it in your experiments.
If you don't feel like making your own container blend from scratch (but then, where's the fun?), rejoy: container blends are the only preblends that are (relatively) easy to find in Europe (lucky you!). Looking for some? Take a look at our supplies finder.
Now that we've seen the different properties a good container wax blend should have, it's time we look into the formulas.
Please remember that the formulas I give here are nothing more than a starting point for your own experiments! Do not hesitate to try and modify the proportions, test with other additives...
And always write down the exact composition of the formulas you experiment with in your faithful notebook. Don't forget to take note of the temperatures as well! It would be a shame to create the perfect container blend and be unable to reproduce it because you can't remember what you put in it...
1 pound of any container preblend.
the easiest way to go if you have access to it. A preblend already contains all the required additives so you don't have to (and shouldn't) add any.
25 parts of paraffin,
25 parts of vegetable shortening,
2 parts of Vybar™.
2 parts of soft microcristalline wax,
use a 100% vegetable shortening only, based for example on hydrogenated sunflower oil
the most simple and natural formula, expensive but highly appreciated.
25 parts of paraffin 259°F MP,
2 parts of Vybar™,
3 parts of soft microcristalline wax.
if you can lay your hand on a low melt point paraffin (see above)
Time to play
Use these formulas as a jump-start, experiment! Have fun and don't forget to always write down what you're using and in which proportions.
Finding your ideal container wax blend takes a lot of experimenting but is huge fun!