What is frosting?

Frosting (also called blooming) is an informal term for polymorphism, which refers to when the wax is in different states at once. It manifests as a white crystalline trail.

When does frosting occur?

This phenomenon only impacts plant-based waxes. Soy and rapeseed waxes are particularly prone to frosting. That being said, frosting is highly unpredictable and can occur at any time during the candle-making process. It may even be the case that in the same batch, some candles frost while others do not.

How do I minimise frosting?

Get the right cooling profile

To minimise the risk of frosting, experiment with your cooling temperatures. The right temperature will depend on your fragranced wax mixture.

Blend with paraffin

Frosting only occurs with plant-based waxes. Therefore, using plant and mineral wax blends substantially mitigates the risk of frosting.

Pour at the right temperature

Our general recommendation would be to pour your wax as close to the congealing point as possible, which is the temperature at which your wax becomes cloudy. This varies from wax to wax and will help your candle to solidify faster.

Why is my wick mushrooming?

Clubbing, or “mushrooming” as it is referred to in extreme cases, is caused by incomplete combustion of the wax and fragrance oil. This can occur when too much fuel is being delivered to the wick compared to the amount of oxygen being supplied, leading to the formation of carbon deposits on the wick. It should be noted that for highly scented candles, clubbing cannot usually be completely avoided.

How do I prevent candles from mushrooming?

Minor clubbing is very common and is not normally a cause of concern. More pronounced mushrooming is often a sign that a candle is overwicked, so down-wicking will reduce fuel flow and should reduce the effect, although this will create a smaller melt pool.

Sometimes it will be necessary to change to a different wick family to reduce clubbing or mushrooming. Most wick families have differing chemical treatments, or constructions, which are suited to different candle systems. For example, LX wicks are best suited to paraffin candles with low to moderate scent loads, whereas V wicks are designed to deal with heavy fragrance loads, even containing brass powder to help vaporise any carbon deposits.

Occasionally, a particular fragrance oil will cause clubbing regardless of the wick used. In such cases, a different wax blend may improve the situation. Not all fragrances are optimised for candles, but as a home fragrance first business, that is our start point.

Which wick should I use with my wax?
The choice of wick will depend on which wax is being used. LX or TG wicks work well with mineral waxes. Stabilo, CL, V, TB, ECO or PGS wicks can be used with mineral or vegetable blends, while VRL wicks are suited to blends containing a high percentage of plant wax.

Why does the wax pull away from my jar?

Candle wax shrinks as it cools from liquid to solid. After the initial pouring, the liquid wax will be in contact with the glass. As the wax cools, the solid wax will break away from the glass surface as its volume decreases.

Wax Selection

Wax Type

Candle wax pulls away from the candle glass because the wax contracts slightly as it cools. This is an inherent property of the wax and cannot really be avoided, so most waxes will pull away from the candle glass to some extent. Mineral wax in particular will have poor glass adhesion. Soy wax can have better glass adhesion but will still pull away to some extent over time.

Temperature

Pouring wax at the correct temperature can improve glass adhesion in some cases. However, wax shrinkage is an inherent property of the wax and cannot really be avoided completely, so most waxes will pull away from the candle glass to some extent.

How do I improve glass adhesion?

Clean Jars

Making sure the inside of the glass is clean and free from release agents can help promote adhesion.Most glass is coated in a wax-oil mixture, called cold-coating.This can cause problems for painting and adhesion.

Pre-heating Jars

Pre-heating candle glasses will improve glass adhesion, but this is normally only temporary, and the wax will usually pull away from the glass over a period of hours, days or weeks.

Pouring Temperature

Pouring wax at the correct temperature can improve glass adhesion in some cases. However, wax shrinkage is an inherent property of the wax and cannot really be avoided completely, so most waxes will pull away from the candle glass to some extent.

Room Conditions

The room temperature should be greater than 20° when pouring candles. If the ambient temperature is too low, the wax will cool and shrink more quickly, and pull away from the glass more readily.

Does my choice of glass impact glass adhesion?

Opaque Glasses

Glass adhesion is nothing to be concerned about if you are using an opaque candle glass. Even if the wax does pull away from the side of the glass, this will not normally be noticeable apart from perhaps a slight gap between the surface of the candle and the side of the glass.

Why is my candle giving off soot?

Soot is formed by incomplete combustion of candle wax and fragrance oils, leading to formation of carbon deposits. Sooting will almost always occur, but in varying degrees. It is usually emitted when the flame is disturbed, either by airflow, excess fuel delivery or poor wick posture. Excessive sooting can be avoided by experimenting with different wick families and sizes. Some wick families are more compatible with certain wax types.

How high is too high for candle flames?

A 30cl candle would typically have a flame height of around 30-35mm. For a 20cl candle, the optimum flame height would be around 25-30mm. A candle flame can be as high as 75mm, but a flame of this height would probably fail a sooting behaviour test and could also fail a fire safety test.

How much oil should I use?

Different Jar Sizes

The size of candle glass doesn’t impact the percentage of oil used. The same percentage of oil can be used in candles throughout a series of different sizes, although each differently sized candle will require a different wick.

Different Preferences

The amount of fragrance oil in a candle is decided by the chandler, and is typically based on the cold and hot throw of the candle. Candles containing larger percentages of oil can be more challenging to wick correctly.

Different Waxes

Plant waxes will generally be able to hold more fragrance oil than mineral waxes. Plant waxes can normally accommodate 10 - 12% fragrance oil without difficulty, but the content can be reduced if required. Mineral wax candles can give good cold and hot throw at 8 - 10% but a fragrance content of less than 8% is not uncommon. Candles with fragrance concentrations of more than 14% are very unusual as they can become very expensive.

Wick Selection

The choice of wick will depend on which wax is being used. LX or TG wicks work well with mineral waxes. Stabilo, CL, V, TB, ECO or PGS wicks can be used with mineral or vegetable blends, while VRL wicks are suited to blends containing a high percentage of plant wax. Overwicking can cause larger flames which can then form larger melt pools and generate more soot. Overwicking is the term used to describe the use of a larger wick than necessary for a particular candle.

What is sweating?

In candle making, sweating refers to beads of liquid oil appearing on the surface of a candle. The technical name for sweating is syneresis and it is caused by the expansion and contraction of wax crystals, which can squeeze oil out of the body of the wax, making it visible on surfaces.

Why does sweating occur?

There are five main reasons why a candle may have liquid on the surface. The first is that there may simply be too much fragrance or essential oil mixed into the wax. This means that there is insufficient space between the crystals to retain the amount of fragrance oil added.
Second, sweating may be a characteristic of the wax itself. Many plant waxes are a blend of fully and partially hydrogenated oils. If cooled incorrectly (too slowly), low melt point ‘alpha’ crystals can form and sit on the surface of the wax as a liquid or slurry. These fat oils can also displace fragrance oils, as there is insufficient space for additional liquids amongst the crystals.
Third, rapid changes in temperature can cause syneresis, especially when moving a candle from a cold location to a warm location.
This can also happen if the oil is added when the wax is too cool, or if the wax/oil is not properly mixed. In this instance, the wax and oil do not form a homogenous mixture and the distribution of fragrance will vary throughout the candle.
Finally, if the fragrance supplier has little experience in candles, their fragrance oils may contain components that are insoluble in your wax. This can be the case when fragrances were developed for other products (i.e. cosmetic products), as fragrances rarely work well in multiple products and should be fine-tuned for the end application.

How to avoid sweating?

- Fragrance load reduction

One of the first steps you can take is to check the wax manufacturer’s fragrance load recommendation. This will be unique to every wax type. As a rule of thumb, however, we would recommend keeping your fragrance load to 6-10%, although some fragrances can be added at up to a 12% load in waxes. Experimentation and testing are key.

-Buy quality fragrance oils, optimised for candles

All Candle Shack oils are developed primarily for use in candles and are subjected to rigorous stability and performance testing. Be cautious if buying fragrance oils that are provided by generalist craft supply businesses, claiming their oils work well in candles, soaps, bath bombs, carpet fresheners, face creams etc. It is extremely unlikely that they will have been properly tested, if at all; especially if they have hundreds of oils.

- Temperature control

Keep a moderate and constant temperature during storage and avoid prolonged storage at elevated temperatures. As a general rule, we would recommend storing your candles at a temperature of 18°C to 25°C. Likewise during production, allowing plant-based candles to cool at ambient temperature will minimise separation vs. attempting to slow the rate of cooling too much.

- Switch waxes

Fragrances react differently and have different solvability in different waxes. By switching waxes, you can try to find one that works well with your chosen fragrances.

What are jump lines?

Jump lines (also known as chatter or stutters) are thin rings or horizontal lines that form along the outer edge of container candles and pillar candles.

Why do jump lines happen?

Jump lines predominantly occur with paraffin or hybrid waxes as they have higher melting points than 100% plant waxes. When wax is poured into cool or room temperature glasses, if the wax temperature isn’t high enough, wax can solidify very quickly when it comes into contact with the jar. In extreme cases, it can solidify in stages, even as the wax is being poured, causing ‘jump lines’.

How do I avoid jump lines?

Choose opaque candles

While not aesthetically pleasing, jump lines do not impede candle performance and only manifest where the wax meets the glass. Therefore, avoiding clear candle jars and choosing opaque ones will hide this defect.

Temperature Control

Jump lines occur when the wax solidifies on contact with the glass, so there are only two ways to prevent jump lines from forming…

- Pre-heat the candle jars

Warming your jars will make it less likely that wax will solidify on contact. The cooler you want to pour the wax, the warmer the glass will need to be to avoid jump lines. The golden rule is that 'the wax should be 10°C above the melt point after it's been poured', especially where it is in contact with the glass. Warming jars means they will subtract less heat from the poured wax. Pre-heating the jars to a known temperature is the best of the two options, as it is repeatable.

- Increase the pouring temperature

Alternatively, heat the fragranced wax in 5°C increments until you find a pour temperature that gives no jump lines. This is a good method if the place where you pour candles is at a consistent temperature, as the process will be repeatable. If using this method, you should still try to pour the candles as cool as possible.

What is tunnelling?

Tunnelling, also known as sinkholes and cavities, refers to gaps or voids that are formed inside or at the surface of a candle as the wax contracts during the cooling and curing process. They are more common in mineral wax than in plant wax.

What causes tunnelling?

Tunnelling occurs when a candle is under-wicked. The wick produces a flame that isn’t strong enough to melt the wax all the way across the top of the candle, so the diameter of the melt pool is too small and remains so for the duration of the candle’s life.

How do I avoid tunnelling?

Double Pour:

The risk of tunnelling can be reduced by using the double-pouring technique. First, fill 70-90% of the candle. After cooling, when the wax has contracted, the second pour fills the candle to the desired level.

Pouring temperatures:

Tunnelling can be avoided by pouring candles at specific recommended pouring temperatures.

How do I fix candles with tunnelling?

Relief hole:

A relief hole can be created by puncturing the wax above a sinkhole after the first pour of the candle. The void can then be topped up with melted wax.

Heat gun:

For tunnelling near the surface of the candle, a heat gun can be used to melt the surface of the wax above the sinkhole. The melt pool formed by the heat gun will flow into the sinkhole and leave a level surface.

What is cracking?

Cracking is often experienced when using plant-based waxes. Cracks can appear on the surface or throughout the candle.
Cracks can appear in different forms. Sometimes cracks occur as shallow localised cracks that form a rough circular shape on the surface of the candle. These concentric cracks often appear above a cavity in the wax. Occasionally, radial cracks can form across the top of the candle, running from one edge to the other and normally passing through the wick area. This type of crack can be deep, often running from the top to the bottom of the candle.

Why does cracking occur?

As the wax cools, it goes through different stages of crystallisation. During those phases the wax can contract and crystallise in different ways, causing cracks to occur. Cracking is a common problem in plant wax candle making, with rapeseed wax being more prone to radical cracks and soy wax, while less likely to crack, tends to produce circular cracks. If candles are allowed to cure in cool environments, they are more likely to crack.

How to avoid cracking?

Temperature control

Keeping adequate and consistent pouring, cooling and storage temperatures is the best way to avoid cracking. Make sure you pour your wax mixture at the temperature recommended by the wax manufacturer. While your candles are cooling, ensure that they are not kept in a cold environment. As a rule of thumb, we would recommend cooling your candles at a steady temperature of 18°C to 25°C for 48 hours. After that, the candles can be kept at slightly cooler temperatures.

Paraffin blends

As cracking is predominantly a plant wax issue, you could choose to blend your plant wax with paraffin wax or switch to paraffin wax altogether.

How to fix cracking

Surface racks can often be removed by using a heat gun for a few seconds to smooth out the cracks. Deeper cracks can also be removed by using a heat gun but they may reappear as the candle cools again.