Greg
Oh, by all means, please do tell.
Greggie--ask and ye shall receive.
I came up with this trick on my first modeling tour. It works fantastic, if you follow the process closely.
1. Cut a piece of sprue to use as a handle.
2. Get a lighter and hold the flame at the end of the sprue just long enough for the plastic to ignite. You will need to hold the sprue in the flame to accomplish it. Once ignited, pull the lighter away and let the sprue burn on its own.
It will look sort of like this. The camera makes the flame look bigger and hotter than it actually is. No matter, it's burning.
3. Let the flame burn for 3 seconds. Do the 1 one thousand 2 one thousand 3 one thousand trick.
4. After 3 seconds immediately blow out the flame.
5. After the flame is out, wait 4 seconds and then press the sprue into the unseen side of the piece. Don't force it. The plastic is soft. Let it do the work for you. Just push it gently until you see the plastic spread out as shown below.
6. Hold the sprue and piece as steady as you can for about 10 seconds. Then set it down to fully cool. It should take only a few minutes to fully cool.
And you are done!
This will not damage the outward facing side as long as you follow my process. If you let the sprue burn too long--it will become hotter--and then it's a guessing game of how long to wait for attachment.
You get a pretty decent bond doing this. I can even do a final soap wash with them attached if you are careful not to stress the connection too much. But--if you do--just follow the same process. NOTE: If you must redo it--clip off the previous melt point because leaving it there messes up the formula. You risk over-heating the piece and you don't get as good a connection. Trust me on this, it's important.
When you are ready to remove the handles you simply bend them away from the piece and they easily pop off. All that remains is a blackened area where it was connected.
I would encourage people to practice on scrap first. The formula is pretty foolproof, but you need to get a feel for how much pressure to exert, and in keeping the piece steady until cooled enough. Trust me. This all sounds harder than it really is. I am giving you all the what nots. But in practice--it is very easy to do. I have been doing this process a long time and it works very well.
Lastly--I would not use this method on very small pieces or--where there is not a lot of plastic to dissipate the heat. The pieces in this post and in my first are good examples of what is safe to do it on.
Oh--and one other thing. The backside of the piece does not need to be flat for this to work. It works perfectly fine on irregular pieces. Like let's say a car engine that his dips and such.