How to Properly Trim a Lamp and Set the Burn Height

Going back into old-fashioned knowledge again here: We’re trying to keep alive an art that is passing.

I was outside the other night and realized the wick in my lamp needed trimming. So here we go…

I’ve collected and restored kerosene lamps, guide markers, and road markers for years and years. I recently realized that the art of trimming a lamp is something that used to be a bit of everyday knowledge for everyone; but the art is getting lost.

You know you have to trim a wick when the top of the flame is shaped like an ‘S’ or is way taller on one side than the other. The top of the flame should be nice and straight for most lamps; this gives you the optimum efficiency and light output. An efficient flame also smokes less.

An aside: This doesn’t apply to lamps with an ‘efficiency’ burner – they were made to tailor the airflow around the wick, and so a good flame on these lamps should have a peak in the center and it’ll be shaped like the bracket key on your keyboard: } These ‘efficiency’ burners have to have the wick trimmed dead straight. You can tell if you have one of these burners because it has a plate on either side of the wick that’s full of holes. “Long-time” burners use a round wick and are shaped like a Y.

So here’s how you trim a wick for ordinary burners:

Open your lamp, pull the glass out (set it aside for washing), and raise the wick until you see the charred end where it’s been burning. Often it’ll look like the top of a mountain range. Take a good close look at the wick while you have the lamp open; it matters for the next things you’ll do.

Get a SHARP pair of scissors and trim the charred area straight off; discard it. An easy way to know that you’re trimming straight off, is to take out the wick raiser assembly, wick and all, and raise the wick a bit. Use the top edge of the wick raiser as a guide.

Now for most burners, take a 30-degree ‘nick’ off each end of the wick. Take off just the edge of the weave. What you get if you don’t do this, is a flame with ‘devil’s points’ on it. The flame is shaped like a capital Y with a point at each end that burns too fast and throws soot when the rest of the flame is set properly. This is because the far edges of the wick pull fuel faster and therefore cause it to burn faster. The rest of the wick will burn down to some odd shape instead of these two edges burning off like you’d think they would. And they don’t burn off fast, either, because they’re better-fed from the fuel fount. Meanwhile, you’re left with a dim lamp that soots up far too quickly.

Back to our story.

Now wind the wick back down, wash the glass with plain soap and water, and reinstall it. If you’re using impure fuels (or if it’s been a while since the lamp was cleaned – often the case with me), then use some Bon-Ami on a wet paper towel to do the scrubbing. Ordinarily I use a paper towel with a squirt of dish soap on it to wash the glass; that way I don’t trash a sponge or dishrag with the soot. The soot is greasy and mildly toxic. Dry the glass if necessary (I usually don’t because I’m going to go burn the lamp right away) and reinstall it. And if you’re going to burn a lamp with wet glasss, burn it low! DON’T burn it high at all until the water evaporates – this a good way to shatter a lamp glass.

Always be mindful of the top and bottom edges of the lamp glass. Even in modern lamps, that edge is seldom finished, and it’s guaranteed to be sharp. The only glass I’ve seen that has that edge finished is Fuerhand (German) lamp glass.

On to lighting and setting the burn height:

Raise the glass and bring the wick up with the wick raiser until it’s up out of the holder about 1/8”. Light it and lower the glass back into place. Set a smallish flame until the glass and the lamp warm up. The flame will actually grow as the lamp warms up and gains efficiency.

Once the lamp’s hot, bring the flame up until it ‘feathers’ at the top. At this point you can often see the lamp smoking. (If you leave the lamp set at this point, it will soot up the glass after a while. If you bring the flame higher, it’ll soot up the glass in a real hurry. I sometimes call this sooty burning ‘the Hollywood Look’ because it’s obvious they don’t have to work by the light of this lamp!)

Bring the flame down until it’s a little below this ‘feather’ point. This is your best burn point. Check the flame height from time to time, especially if you’re outside. If it gets breezy, or if you’re not going to be checking the lamp periodically, just bring the flame down a bit from here to prevent smoking and soot accumulation.

Some lamps like Dietz’ Air Pilot, are lamps made to be used indoors. They have an efficiency burner that will not allow them to work well in any kind of a draft, unless it’s a steady draft; so they’re useless outdoors.

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