Candles have memory?

Factual Questions
1

The “Hints from Heloise” in today’s Houston Chronicle brought up an interesting phenomenon, if it’s true. The question is about “candle memory”. The person stated that candles have memory. They will remember how close to the edge they were burned the first use and forever on they will not exceed that width.

Heloise didn’t state why this phenomenon occurs. She only gave tips on safety regarding burning a candle to the edge. So I bring the question to the best repository of scientific minds I know of.

  1. Is it true that a candle will forever only melt as far as it did on the first use?

  2. How does it do this?

2

I think “memory” is just antropomorphisizing the physics of the candle. It doesn’t remember anything it just behaves consistently.

A radiant heat source like a candle flame follows the inverse squares rule. That means as you get farther away the intensity of the radiated heat is inversely proortional to the square of the distance. For a given candle flame there is a distance beyond which the heat isn’t enough to melt the base wax. That distance will be pretty much the same each time you burn the candle unless conditions of the wick change significantly.

3

Um yeah, what Padeye said. It basically finds a happy medium…a balance and maintains it because of the way the heat causes the rest to melt. It couldn’t burn through the first time, and as the wax collapses, it has even less of a chance because the flame is going to be fairly consistent.

  • this post included just to see how dumb my simple explanation really sounds versus Padeye’s*
4

Yeah, my answer would be better if I did a spell check first and made it simpler to understand.

5

Empirically test it.

Light a wide pillar candle and blow it out after only a 1/4 inch diameter of indentation is made. According to Heloise ( :rolleyes: ), the wick will now burn down through the candle keeping a 1/4 inch diameter as it bores down through the candle.

You can probably guess the outcome.

OTOH, if you keep the same candle burning for, let’s say, an hour. And let’s say it has created a hole 3 inches wide and one inch deep. It’s probably safe to say the the heat being generated will not melt any wider a hole whether you leave the candle burning continuously or blow it out and relight it later.

Peace.

6

Yes, but WHAT IS IT? Don’t mistake the guess for reality.

The only way to know the outcome for certain is by experiment. But there are lots of ways to fool ourselves and block such knowledge, i.e. by saying “we KNOW the outcome, therefore performing an experiment would be a waste of time.”

For centuries everyone knew that an apple would fall much faster than a grape, and performing experiments was a wast of time. Therefore nobody in authority bothered to walk across the room and grab two different-weight objects and actually try dropping them to see what happened. That is, until Galileo started carefully observing nature rather than listening to contemporary theory while remaining as clueless as civilization’s top experts. Modern science was born when the experimentalist viewpoint finally became legit, and the population of overconfident philosophers who dominated all scientific pursuits were shown to be vastly, flagrantly, embarassingly wrong, and so fell into obscurity.

MAYBE a tiny 1cm melt zone has no “memory,” and flame radiation determines the size of a small-sized melt zone. (And maybe a feather does fall more slowly than a cannonball! Yet the slow fall of feathers does not disprove the equal acceleration of different-weight falling objects, the example of the feather only blinds us and keeps us from discovering Newtonian Mechanics. Forget the feather, test a golf ball against a baseball. ) And forget the 1cm melt zone, compare melt zones which are well outside the zone melted directly by flame radiation. Compare a 1" zone with a 1.5" zone. Is there “candle memory” in that case?

How could memory be possible? Maybe fast-hardened wax will melt more quickly than the slow-hardened wax of the bulk of the candle, resulting in “melt-zone memory” where some fluid convection originally carries the melted border well outside the region that the flame could melt by radiation… and that old zone of fast-hardened wax will quickly re-melt in later times. Or perhaps the fast-hardened wax of the melt zone has a different capillary effect on the newly-melted wax, allowing the melt zone to grow fast through previously-melted wax, but only grow slowly through new candle-stuff.

Or maybe the old melt zone is simply LOWER than the flat face of the candle top. The lip of the old melt zone might prevent any wax convection that could cause the melt zone to enlarge past the original diameter. Yet when first lit, fluid convection could deliver hot wax a great distance away from the wick, forming a melt zone which is much larger than one determined solely by flame radiation.

To say “it doesn’t happen”, and then to perform no experiment to verify that indeed it doesn’t happen… that’s called speculation masquerading as knowledge. Also, the (:rolleyes:) is an emotion-based debating trick, an attempt to ridicule and bully others into not asking questions.

Well, I call you on it. Cut out the eye-rolling pseudoscientific tactics. Instead, think like Galileo trapped in a world full of Aristotle-worshippers, and go get yourself a darned large-diameter candle. A few minutes of observation by one thoughful hobbyist beats many centuries of intensive philosophical speculation done by the world’s sharpest professional intellects.

7

Actually I have seen very tall narrow candles develop “blowouts” through the side wall after extended burning. This was probably due to the fact that the candle burns somewhat more slowly once the flame is well down into the candle, due to the slow melting of the interior walls of the channel formed by the retreating wick and flame. The resulting pool of molten wax has more time to act.

It doesn’t happen often because a) most standard candles are designed with a suitable width for their wax and other properties (hey they crank them out by the thousands or millions - vs. art candles which are more experimental and not really meant to be burned); b) it is more common for the extra wax of an inexpertly designed candle to drown out the wick before blowout occurs; and c) regular candles seem to use a harder, higher melting wax than some art candles.

So I’d say that the reason candles burn a fairly consistent width is that they are designed to do so. (But what’s the magic in that?) Blowouts are potentially dangerous, and drownouts annoy the consumer

8

Oops. I should have been clearer. By ‘tall narrow candles’ I don’t mean the standard tapers traditionally used for a romantic dinner. I meant a wider cylinder which burns "down the middle. The last example I can recall was cast and decorated by an amateur (?) candler and bought at a flea market.

9

Here’s the article in question

After some googling, I’d have to say there’s something to this, given that every single commecial candle site I’ve found contains some variation on:

(from here)

No one seems to have a good explanation of why it happens, though.

10

And that’s why I said to empirically test it. You do know what empirically means, don’t you?

I don’t have the time to do the experiment. I just explained how to set it up. When you do the experiment, don’t forget to account for air currents.

But that was a nice rant against the opposite of what I meant.

Peace.

11

It’s not clear? Really?

I wasn’t ranting about emprical testing. I was ranting about eye-rolling sarcasm directed at the person suggesting that candles could display such a “memory” effect. I guess I’m just being a net-cop. When I see a teacher using sarcasm to make a student feel stupid for asking a question, I absolutely SEE RED. When strangers on web forums do the same, I only get mildly annoyed, and perhaps deliver a rant.

So here are my own questions. They should clarify condictions and satisfy your original objection.

Given an immensely wide candle with a normal wick, approximately how large can the “melt pool” grow? Does room temperature have a large effect?

And, what’s the minimum diameter for a melt pool?

If the “memory” effect is real, is it the raised lip which prevents the melt pool from growing past the old boundary? Will lowering that barrier make a difference? Or is something more interesting occurring?

I hadn’t heard about ‘candle memory’ in the past. Time to go get a big block of paraffin from the junk collection in the garage…

12

There might be a bit of something here. Imagine 2 candles, one burned for 3 hours the other for 1hr. The 1hr candle will have a smaller ‘melt pool’ than the 3hr. The melt pool will be at a lower level than the rest of the candle, as wax will have been burned, and from only the melt pool. This leaves us with a step profile, a lip if you prefer, from the original candle to the melt pool level.

When you relight the candles, they will melt wax out to the edge of the melt pool, but might not melt the wax above the melt pool (wax outside the melt pool) as readily. The wax above the melt pool will not be in contact with the hot wax as directly as wax at the same level as the melt pool.

This would be fairly easily tested, I would think. I think it is the lip that affects the melt pattern. Cut the lip off and any effect should vanish.

13

The person in question, whom you are so valiantly defending from the slings and arrows of sarcasm is Heloise, as in Hints from Heloise ( :rolleyes: ).

14

I’m not familiar with this Heloise person, but it appears that she basically provides household tips. Does that really warrant a rolleyes? If she’s known to be frequently or unapologetically wrong in her advice, then that’s another matter, I guess.

Also, as stated in the OP and in the actual article that I linked to above, it’s ‘Susan, Bristol, VA’ who brought up the ‘candle memory’ issue - Heloise doesn’t really address it at all, just saying “And follow the directions on a candle’s label (which usually say to burn it for a specific time period the first time).” Which seems reasonable enough.

And again, as I mentioned above, every commercial candle webpage I found that has a ‘tips’ section mentions the candle ‘memory’ issue. Could they really all just be propogating a baseless myth? Or could it be that they know their stuff when it comes to candles?

15

Hints from Heloise is not a scientific journal.

That’s why, in my post on the need to do empirical research, I rolled my eyes at using Heloise as a source for the proposition that candles have ‘memory.’

Sheesh, I’ve never seen so much angst over the rolling of eyes.

:rolleyes: :rolleyes: :rolleyes: :rolleyes: Take that! :stuck_out_tongue:

16

Actually, if you read the linked article, Heloise is not the source of the information:

If you’re going to roll your eyes, do so at the right party.

17

The quoted info from the National Candle Association ( :rolleyes: ) is not scientific and terribly unhelpful to the question of candle ‘memory.’

18

OK, very brief testing with 1.5" dia. candles shows NO memory effect. I tested melt-pools of ~1/2" and ~3/4".

Extremely strong convection appears even though the melt-pool is extremely shallow. A few motes of soot show the flow, and they move back and forth from the wick to the melt pool edge about twice per second, covering about 1/4" from wick to edge. I remember noticing this effect as a kid, but at the time I didn’t understand what I was seeing. No doubt the strong convection distributes heat evenly across the entire melt pool, at least with the small pools I observed.

This might hold a key to any “memory” effect: if the second melt pool has to re-heat a large volume of the candle, then by the time it reaches to the prior border, the wick will have burned lots of the liquid oil, and the level of the pool will be significantly lower when it reaches the raised lip. I would imagine that the temperature of the room would have a large effect (“memory” might only appear on cold days.)

NOTE It’s halloween, so big packages of inexpensive jackOlantern candles are plentiful in stores.

However, the candles I used were case with a slightly convex face, maybe 1/10" higher in the center, which produces a melt pool that sticks up above the neighboring solid surface and would greatly affect the structure of any “lip.” Wide candles usually have a valley in the center (the wax contracts as it freezes, so we tend to get a little funnel shape in the center of a wax block as it freezes.) If “memory” is real, then perhaps the convex design is an attempt to eliminate the effect. I guess I’ll have to chuck some of the things in the lathe and make flat faces with artificial “lips” of various heights.
I’ve just made a 5" candle in a bowl so I can watch the large melt-pool growth. Interesting: paraffin from the grocery store stays ice cold in a 1KW microwave oven. The glass bowl was the only thing heating up!

Obviously it could go either way, with the power of urban legends conflating the observational powers of Candle Professionals. :slight_smile: Should we put our faith in the power of human stupidity, or in the power of good ideas to spread widely? The scientific community makes errors too, but they tend to be the exact opposite: emotionally biased disbelief rather than emotionally biased belief. If a group is made of people who (as students) were afraid of attracting ridicule from classmates for being gullible, they might swing too far the other way and end up as closeminded dogmatists. Flee the type-II errors? End up making lots of type-I errors!

19

Candle memory seems to exist! However, it only happens when the “hole” in the candle is larger than 3/4" and smaller than 2" diameter. However, there are other effects which masquerated as candle memory. Also, my testing was done on cast paraffin candles with a small string wicks in a 70degF environment, so maybe things will different under other conditions.

Here’s the most interesting part.

With a very wide candle, if I artifically force the melt-pool diameter to become larger than two inches, it will be unstable, and the size contracts to approximately 2" and then stops shrinking.

On the other hand, if I dig out a narrow hole surrounding the wick in order to force the melt-pool to be very small, it will be unstable, and it will expand to between 3/4" and 1" diameter… and then stop growing.

Apparently there is a range of sizes of hole-diameter where once a surrounding “lip” has formed, the melt-pool will neither grow nor shrink in diameter. On the other hand, if your huge candle ends up boring a 2" diameter hole through the center… that’s normal. The flame doesn’t put out enough energy to make the melt pool bigger than that.

I had trouble producing a smaller candle-hole simply by lighting a candle and then blowing it out prematurely. When re-lit, the melt pool grew right past the older diameter with no problem. Only if the melt-pool had dug a hole for itself a little deeper than about 3/16" deep, only then would the pool be unable to eat its way through the surrounding “cliff” and continue to expand to 2" diameter.

One possible conclusion: people light candles and then REPEATEDLY blow them out prematurely. This would let the flame consume lots of wax and eat its way down into the candle during each burn-period, rather than creating a 2" melt pool during a much longer burn.

Another possibility: cheap candles. I encountered candles made from rammed-powder wax rather than cast solid wax. They’re full of air, and the flame eats rapidly downwards into the wax much faster than it does with a solid cast block of paraffin. Perhaps if these kinds of candles were blown out prematurely, they would become trapped in the “small melt-pool” mode. And perhaps the lower limit would be less than 3/4" diameter (but I didn’t test these things.)

Another possibility: cold environment. At 70degF the melt-pool would grow to 2", but it grew very slowly as it approached its final size. If the room temperature was far lower, the melt pool and the resulting hole would no doubt be significantly smaller, yet this would have nothing to do with “candle memory.”

Another interesting bit: convection of liquid wax in the melt-pool delivers hot wax all the way to the border of the melt-pool. The hot wax even crawls up a steep incline as a thin film before settling deeper to the solid wax surface and returning inwards to the center. I put lots of bits of soot as tracer particles in the melt pools, and could watch the high-speed outward motion of the surface layer of the liquid wax (and the low-speed opposite motion of wax throughout the rest of the volume of the melt pool.)

20

I have caught her articles to be in error before. In one particularly lazy column, she just prints others’ advice, and she does not correct their foul errors. Someone suggested that after turning off the oven after baking, the excess heat could be used to warm the house and reduce energy consumption (during winter) by leaving the door of the oven open.

Except in houses with built-in ovens with a side touching an outside wall, the excess heat has nowhere else to go, regardless of door position.

That certainly warrants rolly-eyes, but I will refrain for the sake of the boards.