What Does Candling Mean?

What is Candling?

Candling is the act of placing a light source, such as a candle or bright light, behind an object to determine its contents or look for imperfections. The term comes from the practice of holding a chicken egg up to a candle flame to observe what is inside.

The origins of candling are unclear, but it has been used for centuries in various applications like beekeeping, gemology, and medicine. According to this source, the earliest references to candling date back to Ancient China, where they would pass eggs in front of a flame to check their freshness. Others state candling began in Ancient Egypt with examining eggs for fertility rituals.

Today, candling techniques have been modernized with bright light sources, but the principles remain the same. It is a simple, non-invasive way to peer inside an opaque object and gather information about its contents and quality.

How Candling Works

Candling utilizes a bright light source to illuminate the interior of an egg or other object. When the egg is placed near the light, the light shines through the shell and reveals the inside of the egg. The principle is similar to holding a flashlight behind your hand to see the light passing through your fingers.

According to the University of Illinois Extension, “A bright concentrated light source is needed for successful candling. Light passes through the shell of the egg and reveals on the outside an outline of the interior of the egg.” https://ourhomesteadadventures.com/why-we-candle-chicken-eggs/ The inside of the egg absorbs some light, while other areas allow light to pass through clearly. This creates a “shadow” that reveals the contents of the egg.

Candlers were traditionally candle-lit devices, but modern candling uses electric lights. The key is having a concentrated, high-intensity light source to adequately illuminate the interior of the object. The egg or other item is held gently near the light to permit light to pass through its shell or outer layer.

Candling Eggs

Candling eggs refers to the process of shining a bright light through an egg to observe the embryo inside and determine if the egg is fertilized and developing properly. This technique has long been used by poultry farmers, backyard chicken owners, and egg collectors to check the fertility and growth progress of eggs during incubation without cracking them open.

Candling takes advantage of the translucent nature of egg shells and allows the candler to see the size of the air cell, the network of blood vessels, and the developing embryo inside the egg. It is usually done starting on the 7th day after the eggs have been set in the incubator and then every few days thereafter until hatching. Candling can identify clear, fertilized, and rotten eggs.

A bright focused light source like a flashlight, candle, or purpose-built candling lamp is used. The egg is held up in front of the light and rotated to get a complete view inside. Clear eggs with no veins or embryo present indicate an unfertilized egg. Fertile eggs will show a small network of veins radiating from the embryo which increases in density over time. Darkening air cells, changing shadows and movement are also signs of a growing chick inside. Any odd shapes, blood rings or mold indicate a rotten egg.

Candling is important for maximizing hatch rates since it allows chicken breeders to remove unwanted eggs early on. It also provides a fascinating glimpse into the mysterious development happening inside the egg before hatching day. With some practice, candling can be used to determine fertility within 24 hours, predict hatch dates and even gender.

Source: https://poultrykeeper.com/incubation-brooding/candling-eggs/

Candling in Beekeeping

Candling is an important practice in beekeeping that allows beekeepers to inspect bee colonies and honeycomb without disturbing the bees. To perform candling, the beekeeper will use a bright light source behind the honeycomb to highlight eggs, larvae, sealed brood, food storage levels, and other details inside the hive. According to Bee Natural Ear Candles (http://linetap.com/beenatural/), candling with beeswax candles has been used for centuries as a non-invasive way to monitor hive health and productivity.

When candling a colony, the beekeeper will carefully remove frames from the hive and hold them up to the light. Areas of capped brood will appear as solid blocks of wax, while open cells containing larvae will look like small white grubs. Empty cells are translucent, making it easy to gauge the food stores. The technique enables the beekeeper to assess the queen’s egg laying pattern as well as spot any signs of disease or hive pests without upsetting the colony.

Candling is often done using a bright flashlight or electric bulb, but beekeepers can also use beeswax candles. The soft illumination enables them to get a clear picture of what’s happening inside the frames. According to Natural Ear Candle (https://www.pinterest.com/pin/443675000851815259/), the warmth from the flame also helps calm the bees. Candling gives apiarists valuable information to support the health and productivity of their hives.

Candling in Gardening

Candling is a technique used by gardeners to check on the progress of seedlings without disturbing their development. It involves shining a bright light through seedling containers and leaves to observe root growth.

Candling is particularly useful for monitoring delicate seedlings started indoors or in greenhouses. The light passes through the soilless potting mix or transparent containers, illuminating the entire root system. Gardeners can clearly see the size and distribution of newly formed roots without uprooting the plant.

Regular candling enables gardeners to identify problems early before they become visible above ground. It can reveal issues like poor germination, inadequate moisture, obstructed roots, or diseases. Candling also helps determine when to transplant seedlings into larger containers or the garden by evaluating root development.

The ideal time to candle seedlings is in the evening or night when it’s dark. A bright flashlight, headlamp, or portable LED light panel held close to the soil provides the best illumination. Candling every few days allows close monitoring of root growth over time without stressing young seedlings. It’s an easy, non-invasive way to ensure healthy seedling development.




candling eggs reveals what's inside without cracking them open to check fertility and embryo growth.

Candling in Medicine

Candling has been used for therapeutic purposes in ancient and traditional medical systems for thousands of years. Some modern medical practitioners incorporate candling as part of holistic or complementary medicine approaches. One area where candling is sometimes applied is in ear, nose and throat medicine. According to one source, “The practice of ear candling has recently become popular as an alternative therapy. Some promoters say it is an ancient technique used by many cultures to remove earwax and impurities from the ears.” https://www.tribemagazine.com/board/threads/getting-your-ears-cleaned-out.24810/

Candling practitioners claim it can remove ear wax buildup and other blockages, improve hearing, alleviate headaches, and more. It may also be used by ENT doctors to check for potential cysts or growths in the ear canal. However, mainstream medicine considers candling unproven and potentially risky. According to the FDA, there is no scientific evidence it removes wax or improves health, and it may lead to burns or other injuries. Patients should consult their physician before trying candling.

Candling for Gemstones

Candling is a technique used by gemstone dealers, jewelers, and collectors to inspect the clarity and quality of gems and minerals. It involves shining a focused beam of light through a gemstone to identify inclusions, fractures, color zones and other internal characteristics.

To perform candling, the gemstone is placed table-down on the tip of a candle flame or other concentrated light source. The light passes through the stone, projecting an enlarged shadow image of the gem’s interior on a white sheet of paper or light screen. Features like clouds, veils, and fractures become visible. Rotating and tilting the gem reveals the full range of internal features. Magnification can further enhance the inspection.

Jewelers use candling to grade diamonds and determine a diamond’s clarity per the GIA grading scale. For colored stones like rubies, sapphires and emeralds, candling reveals alterations and treatments. Gem buyers often candle stones to verify authenticity and screen out lower quality gems or synthetics. Candling also aids in faceting rough crystals by revealing internal fractures and cleavage planes.

While basic candling only requires a candle, specialized candling devices like diascopes, fiber optic light sources and UV lamps allow more detailed analysis. Careful inspection by candling remains an essential gemological technique for appraisers, cutters and collectors alike.(1)(2)

Candling Safety

When candling, it is important to take proper safety precautions to avoid potential risks and damage. One of the main safety concerns with candling is the risk of eye injury from exposure to the bright light of the candle flame. Staring directly into the flame, even briefly, can potentially cause retinal burns and permanent vision damage.

To prevent eye injuries, proper eye protection should always be worn when candling. Welders goggles or other protective eyewear will shield the eyes from the intense light. It is also critical to avoid looking directly into the top of the candle as it burns. Position the candle off to the side and focus your eyes away from the top of the flame.

Additionally, the heat generated from the candle poses a burn risk. Keeping the candle in motion and not allowing it to remain stationary for too long can help dissipate heat. Candles should be held at a safe distance from the skin and flammable materials. It is also wise to keep a bowl of water nearby in case the candle needs to be extinguished quickly.

Proper training on candle handling technique is also advised. Attempting candle treatments without sufficient experience puts you at greater risk of burns or eye injuries. With the right precautions, candling can be performed safely, but should not be attempted without awareness of the potential dangers.

DIY Candling

Candling is a fairly simple process that doesn’t require expensive or complicated equipment. With just a few household items, you can make your own effective candling devices at home.

The most basic candling setup involves a bright focused light source, a way to block out other light, and something to hold the egg or other item being candled. Here are some easy ways to build your own candler:

  • Use a flashlight or headlamp covered with red cellophane as the light source. The red light improves visibility. Create an enclosure around the light using a cardboard box with a hole cut out to view the egg.
  • Attach a small LED flashlight to an empty toilet paper or paper towel tube. Cover one end with red cellophane and the other end can be placed against the egg.
  • Cut a hole in the side of a shoebox. Cover the hole with wax paper and place a bright flashlight inside, pointed toward the hole. Hold eggs against the wax paper to candle them.
  • Make a viewing chamber from PVC pipes and connectors. Place a small light inside and cap the ends. Cut a viewing hole and slide eggs inside to check their progress.

With creative use of available materials, it’s easy to build an effective candling device at home. The key is controlling the light and minimizing ambient lighting to get the best view inside eggs or other objects being candled. A basic handheld candler is all you really need to start inspecting eggs and bee frames using this traditional technique.

For more candling inspiration, check out this backyard chicken forum thread with DIY setups.

The Future of Candling

Modern technology continues to revolutionize candling techniques with new innovations like automated or digital candling. One example is Laser Life®, a laser candling system that can differentiate live from dead embryos and rotten eggs with more precision than traditional candling methods (https://www.ecat-id.com/en/products/egg-candling-analysing). Laser Life allows hatcheries to improve productivity by removing unwanted eggs earlier in the incubation process.

Other cutting edge candling devices use infrared thermography, ultrasound technology, or transillumination imaging to evaluate egg development and quality more accurately (https://poultry.ceva.com/app/uploads/2023/07/HATCHERY-DATA-SUPPLEMENT.pdf). These technologies help automate egg candling and provide more in-depth data than traditional methods.

As technology continues advancing, future candling systems may incorporate AI and machine learning to further optimize the process. The improved insight from modern candling enables greater efficiency and hatch rates in poultry and other applications.

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