I've mentioned this subject before elsewhere on a message board far, far away in cyberspace, but there may be a few readers who will still find the subject interesting, namely, how to describe the differences between steel rebars driven into the ground for boundary markers without pulling each and every last one out of the ground, cleaning it up for photography, and carefully resetting it in the same position as found. This particular survey was made in connection with a lawsuit that was in progress, so the method really needed to be one that it could not be plausibly claimed could have shifted the position of the marker by mistake.
Part of the problem was determining what the common characteristics of the rebar markers were that could be shown to have been in place at some early date prior to development. It wasn't a stretch to think that other bars of the same pattern and apparent age were also attributable to the same surveyor.
As it turned out, taking rubbings of the pattern of deformations on the bars was fairly easy and effective as documentation. The technique consisted of just cutting some small slips of bond paper, wrapping them partly around the bar and rubbing with a graphite stick to darken the protruding ribs and deformations.
Here are some examples of similar groups of rebars that were found in place in that subdivision:
BTW a possible variation on this technique for wet conditions might be using a piece of heavy-duty aluminum foil instead of the white paper, and just pressing the foil onto the bar to pick up the pattern of deformations. It might work for stamped lettering on tablets as well. I've never never tried this, but it seems to me that you could photograph the imprinted foil with a scale to record the results.
dental alginate
Do the rebars start purring loudly and kneading when you rub them?
> dental alginate
That's the non-flexible molding plaster? How well do you think that would work on the corroded surfaces of rebars and in a vertical orientation?
As with many other things related to land surveying
> Do the rebars start purring loudly and kneading when you rub them?
Well, as with many other things related to land surveying, it depends. I do know that one attorney exclaimed "this is CSI stuff!" He hadn't evidently previously known that otherwise anonymous rebar stakes weren't all created equal.
As with many other things related to land surveying
Have you been able to match the deformations with a particular mill? And watch out for that contaminated Mexican rebar. That stuff should be really easy to track.
As with many other things related to land surveying
> Have you been able to match the deformations with a particular mill? And watch out for that contaminated Mexican rebar. That stuff should be really easy to track.
Those examples were from 1954 as I recall. So almost certainly they were all from domestic rolling mills.
As with many other things related to land surveying
Interesting, I was just working a difficult survey in a large 1954 subdivision last week. I believe the original monumentation was 1/2 inch iron pipe, with the porcupine's mix of rebar and other monuments being retracement surveys over the last several decades. I found two reinforcing bars that had virtually no magnetic signature.
Other than taking your rubbings, have you found any reference materials to help you interpret them?
As with many other things related to land surveying
> Other than taking your rubbings, have you found any reference materials to help you interpret them?
Sure, there are other clues that would identify bars of comparatively modern origin. The marks indicating the mill, grade, and size would be potentially very good clues as to age if the bar was rolled after about 1948.
As with many other things related to land surveying
> Those examples were from 1954 as I recall.
I cheated and looked at the file. They were apparently set in 1957, not 1954.
> > dental alginate
>
> That's the non-flexible molding plaster? How well do you think that would work on the corroded surfaces of rebars and in a vertical orientation?
Kent,
I think he meant that you should try it in the aluminum foil impression.
BTW Kent,
Is a rubbing bar similar to a massage parlor? I guess both are for fun and profit at least.;-)
glenn, that's just the funniest. hope kent's not blushing too badly
> Is a rubbing bar similar to a massage parlor? I guess both are for fun and profit at least.
Well, I was originally going to use the word frottage in the thread title, but I calculated that it would be too obscure for many readers. Now, are we to understand that you expect to leave a massage parlor with more money than you had when you came in? :>
> > Is a rubbing bar similar to a massage parlor? I guess both are for fun and profit at least.
>
> Well, I was originally going to use the word frottage in the thread title, but I calculated that it would be too obscure for many readers. Now, are we to understand that you expect to leave a massage parlor with more money than you had when you came in? :>
Actually, frottage can be interpreted as double entendre as well.
Yes, you understood that correctly. I'd like to think that my expert services are so in demand that I would be paid rather handsomely.:-P
> Actually, frottage can be interpreted as double entendre as well.
Isn't it understood that the thread that deals only with some dry, technical matter will never take off the way that one involving, say, volumptuous women and odd customs will?
> > Actually, frottage can be interpreted as double entendre as well.
>
> Isn't it understood that the thread that deals only with some dry, technical matter will never take off the way that one involving, say, volumptuous women and odd customs will?
Touché. I will concede that.:-)
the secret of alginate....
I was thinking of using the dental alginate to take moldings from caps, but you could expose a portion of the rebar and pour the dental alginate right on top and around the rebar.... presumably there will be a small hole around the freshly exposed rebar that will contain the alginate while it sets. The alginate is rubbery when it sets and plaster can be poured into the alginate to create a durable mold.
the secret of alginate....
> The alginate is rubbery when it sets and plaster can be poured into the alginate to create a durable mold.
Oh, so the dental alginate is a flexible molding compound? It sounds much more time-consuming than rubbings, but there might be cases where it would be warranted, I suppose. Is it fairly widely used in California?
