The seat post had been cut off and hammered down the tube, picture one isn't brilliant but you can just make out the top of the old seat post.
The cork is a bit of 19mm silicon hose with an expander in one end. An old head bolt and a few bit's of scrap plus a bit of threaded tapered scrap did the job. The cork just needed tightening by hand to seal, Picture two is clearly the cork.
The funnel is a bit of brake pipe, a scrap of tube and an old syringe. The brake pipe is ground to a taper, wrapped with ptfe tape and screwed into the bottle bolt hole, screwed in gently as it just has to stay in place[no threads were harmed in the ******* of this seat post]. The syringe is taped to the top tube, I just poured the caustic in to the syringe. Picture three and four show the funnel.
I mix caustic by temperature/feel, it doesn't want to be to hot, otherwise it will boil when it meets the ali. Because I videoed some of this I stuck a thermocouple in the caustic, to see how hot I was mixing it[just trying to be flash] about 50º with the caustic in it was about what I usually mix it to. The water had come out of my dehumidifier and was whatever the temperature was a few weeks ago.
I poured 100CC in to the seat tube, I poured it in at about 4pm. The seat tube got hot but stayed touchable, it was still hot a few hours later[still doing something]. It had started cooling down when I went in for dinner at 7pm so I left it overnight. The next day I emptied the tube and scraped the clag out of the tube with a welding rod. Then I re-corked it and filled it with cold water to flush as much of the crap out as I could. Picture five is what it looked like when I drained the seat post, what you see in the seat post is the clag, which scraped out with an old welding rod bent into a loop.
I mixed another 100CC of caustic. This time I mixed it a bit hotter, after measuring the temp I figured I was doing it a bit cold;-) I mixed it and the temp was 70º. I poured it in and it boiled and steamed out of the other bolt hole, damaging one of the stickers;-( Oh well not the end of the world. I poured a bit of cold water in to bring the temp down, only 10 cc or so. It still felt hot a few hours later and I gave it another few hours then drained it. I scraped the clag out of the tube with an tube with my trusty old welding rod and washed it with fresh water. I had some black clag in the lin bin I had drained it into, but no seat post anywhere.
I twisted a welding rod and some rag up, like a bottle brush and with a cordless drill I gave the tube a clean. I poured some lanolin/white-spirit
in the tube to stop it rusting. Picture 6 is the clean seat post
I would have to guess at the amount of caustic used, I would guess less than a few hundred grams. When mixing the caustic I just sprinkle a little in the water and then swirl the water around till the caustic is dissolved. If you chuck in too much it will boil and climb out of the pot, if your holding it it will burn your hand, I know from past experience. So you just sprinkle a little in.
