penetration test penetration test

Woodworking Experiments

Dye penetration experiments

When my supplier ran out of commercially stabilized pieces for my "thistle" bottle stoppers, I turned to usenet groups for another source. It was suggested I dye my own by someone who didn't quite understand the problem.

The problem

The problem with just dying the piece after it's turned is that it has to be turned again. Confused?

To make my "thistle" stoppers, I turn a green piece for the bottom of a thistle, drill a 5/8" hole in it, then a 5/16" hole down that. I then turn the top out of either dyed burl or purpleheart with a 5/8" tenon to fit into the green piece. The two halves are then glued togehter and then turned to final shape.

It's that turning to final shape that creats the problems. If I just died the green piece after initial turning, I'd cut right through the dye when final turning.

After the problem was properly explained, discussion turned to the penetration rates of dye and whether I could get the dye to penetrate far enough for my needs. I remembered an article I'd seen on someone "stabilizing" pen blanks with minwax finish in a vacuum, and set out on these tests.


All the pieces here are off the same piece of maple burl. The largest piece is about 1.5" in diameter and 1.5" tall. The smallest is perhaps 3.8" on a side and 1" long.

My Test Rig

My test rig.My test rig is a simple 1 gallon glass jar with a hole drilled in the lid. A few brass fittings connect the jar to the vacuum pump through a valve. I would pull the jar down to a vacuum for about an hour, sometimes less. Not having guages I used the bubbles coming out of the wood as a guide- closing the valve and shutting off the pump when the bubbling stopped. The jar would hold a good vacuum at least 24 hours. Even after opening the valve the lid was difficult to release until the seal was broken. (opening the valve didn't completely release the vacuum, just let in whatever was in the vacuum hose)

Test #1. TransFast Dye dissolved in water, 1.5hr soak

Almost no penetration of the Transfast. The piece here shows nice surface color, but basically no penetration. This block is about 3/8" (8-9mm) on a side.

Test #2. TransFast dissolved in alcohol. 13hr soak

transfast in alcohol didn't penetrate either.Yes, I know TransFast is supposed to only be soluable in water. But it at least stayed in suspension in alcohol. This piece shows a *little* penetration near the surface, but not nearly enough consistency or depth.

Test #3 TransTint in alcohol under vacuum. 3 hr soak.

This is more like it. This block is about 3/4" (16mm) tall and showed solid penetration on 3 sides (you're looking at a face that was cut at a 45° on a corner. This approach shows promise.

Test #4. Transtint in alcohol under vacuum. 13 hr soak.

good penetration under vacuum for 13 hours. This stopper base shows dye throughout.Increasing the soak time to 13 hours and tossing in some full-sized stopper bases basically had the piece (similar in size the test #3's piece) dyed throughout. Places where it's not died are a consequence of it being a burl- some parts just don't seem to take dye. On turning the stopper bases I found it to be quite a "light/dirty" green, but never turned through the dye. One piece had a catch and I sawed through its middle (other pic). Dye was throughout.

Test #5 Transtint under vacuum, 24 hour soak

This is the extenstion of tests 3 and 4, but for a kaleidescope block (about 1.5" thick by 2.25" square). I soaked the piece for 24 hours, then let it dry for 24 hours, then glued on the purpleheart and let that dry for another 12 hours. When I drilled the hole down the center it was still *wet* with alcohol. I'd say it had complete penetration. A picture of the completed Kaleidescope is here.

Test #6. Stronger TransTint under semi-vacuum, 6 day soak.

I was heading out of town for a sailboat race (Thistles, of course) and wanted to improve the color I was getting in the pieces. So I added more color to my dye, dumped 6 blocks into the jar pulled down the vacuum and left. When I returned I found leaks had compromized the vacuum, but the pieces show better (stronger) color after drying for 24 hours and being turned/drilled.

Test #7. Strong TransTint (same dye as #6 in open air, 3 hour soak.

Mostly trying to test whether the alcohol or the TransTint could be responsible for the better penetraion in addition to/instead of the vaccuum. This test gave basically the same results as #1- nice surface color, little to no penetration.

Test #8. Strong TransTint, open air, 24 hour soak.

surprising penetration at 24 hrs in air.Extension of test #7 with surprising results. I'd expected results similar to #4, but this shows great penetration through. When I pulled it out the block was barely floating. Makes me wonder if most of the speedup you get with the vacuum could be obtainted by adding weight on top of the wood to force it down.

Test #9. TransFast dissolved in water, under vacuum, 24 hour soak.

TransFast+ water under vacuum showed great color thorughout. Direct comparison to #5. The TransFast didn't penetrate as deep, but the color is shows is much brighter inside the piece. I wonder if the pieces of TransFast aren't larger, which would help explain their slower penetration rate and seeming brighter color inside the piece.