Making Casts/replicas Of Bms, Possible? Options

[Crusso]

Ok, being a CSI/Mythbusters watcher I came up with this idea.... Is it possible to make a cast of a benchmark (would be a negative or reverse of the BM) then go home and cast the positive so you'd have a BM relica?
Seems to me with all the casting materials on the market and the fact that BMs have survived in the elements for so many years that there should be some non-destructive casting materials around that would yield good results. Anyone have any thoughts?

[Photobuff]

I know you can get casting kits where you pour silicone rubber over the item to be cast, then fill it with the plastic resin of your choice. Can't see why that wouldn't work. You can also go through another couple generations to make a plaster or sand mold, and cast in metal. Cool idea

[Zhanna]

Interesting ... I have just been working on a web page demonstrating my process for making molded chocolate benchmarks! So far I have used only the benchmarks in my collection (destroyed marks that I was instructed to remove, or unused disks that were sent to me), but I was thinking that the same process could be used in the field to create a mold of a particularly interesting mark.

For my molds, I have used a two-part silicone molding compound. You simply mix the catalyst and base together, then form the resulting "goo" over the shape you wish to replicate. After about an hour the compound cures and you have a sturdy, flexible, heat- and cold-resistant mold. I used a food-safe formulation because my intent was to make chocolates, but if you don't plan to use the molds for food products there are lower-grade (cheaper!) molding products available that will work just as well.

I'll post a link to my page when it's ready.

~Zhanna

http://surveymarks.planetzhanna.com/

[Edit: fixed typo]

This post has been edited by Zhanna: Jan 5 2006, 12:00 PM

[Crusso]

I was checking some websites and the silicone seems to be the way to go. Only problem is they all say roughly 16-24 hrs cure time.
I think it would be kinda hard to leave the goo sitting there covering the BM for that amt of time. ( I can see explaining that one to the cops!)
Zhanna, u stated something about a 1 hr cure time. What kinda stuff (brand, formula, etc) is that? Any help would be appreciated. Thanks

This post has been edited by Crusso: Jan 7 2006, 11:29 PM

[Photobuff]

You should be able to do even better than that. I don't know what the stuff is, but think about the disgusting stuff your dentist uses to take impressions of your teeth. They make ceramic replicas and even gold crowns from those, and the glop hardens in a few minutes.

[Zhanna]

[Zhanna]

[kc2ixe]

heh - all too high tech

At least on horizontal marks - they have no undercuts, so you should be able to spray them with something like pam, or silicone spray, build a small cardboard dam around the mark, and just pour in plain old plaster - wait 20 minutes or so, and lift up - now you have a plaster mold

[mloser]

But then if you are making chocolate treats you need a flexible mold so you can remove the molded benchmark from the mold without breaking something.

[Klemmer & TeddyBearMama]

But if you want something more permanent than chocolate, you probably want plaster. So - pick your method, I guess..... I'd like to do the first benchmark I found & logged. It was a virtual geocache, before GC.com started the benchmarking section: Rose, or as a virtual cache: ... huh! can't find it as avirtual! I know I didn't imagine it... I guess it was deleted as a virtual when they started the benchmark section - or something.....

[mloser]

I think Zhanna is correct no matter what you want as an end result. If you make your first mold out of rubber you can cast almost anything in it, except hot metals. Then you will have to go to a lost-wax method or sand casting. If you consider plaster to be edible (consider it a placebo!) you can make both candy AND plaster benchmarks. Another possibility is epoxy resin. You might want to use a separate rubber mold than your candy mold though.

I am fascinated by the casting process but don't have any benchmarks I really want to bother duplicating.

[Cape Cod Cacher]

USE A RELEASE AGENT !!!!!!!
Butcher's Wax works pretty well to seal up the little cracks & crevices in the concrete, go heavy. Use a toothbrush to apply it on the disks after a light steel/bronze wool to clean it off, and then buff it out. A bit of modeling clay is a good tool as well, keeps casting goo from finding under-cuts. I'm not too sure how well any casting will be recieved, it's a pretty messy process. I've been making molds for 20 years (some of you may be walking on some of my past efforts), and it does get nasty. 98% of casting materials have SOME shrink, even chocolate. Temperature is a major factor too. Too cold/hot can make for a nightmare. A quick and dirty cast can be made using thin Bondo and an acid brush. Pattern wax would work in the right environs. Practice before you go out in the field, a few benchmarks with globs of blue silly-cone or plaster perma-attached to them won't make us look too cool.
I use "industrial", "professional" stuff ( read : pricey, I get it a couple years past date for free from clients), I'm curious how crafty shop or hobby stuff works. I know of some things used in Model Railroading that can take casts of rocks. Hmmm.
Good luck, too cold in New England to play with this too much now.

[Crusso]

I have a practice BM at home to use. I seem to be leaning toward the silicone stuff. Gotta wait till it warms up though.

[travisandalisa]

I am currently in dental school, and have been thinking about making a mold of a benchmark for a cache idea. I read through this thread about materials to use. It is true that dental alginate is only good for a short while. It starts to shrink within an hour as it loses water. However, there are many other impression materials that we use. Each one has different consistencies and strengths when it sets. I am thinking about buying a tube of polyvinylsiloxane from the school and trying it out. It has great detail reproduction abilities and can be used repeatedly. Maybe your local dentist would let you buy a tube from them.

[Cape Cod Cacher]

Please please please clean up your mess!
Pahzalusta to Zhanna

[Zhanna]

As promised, here's a page demonstrating the mold-making process for my chocolate benchmarks:

Zhanna's Chocolate Benchmarks

Enjoy!

~Zhanna

http://surveymarks.planetzhanna.com/

Cape Cod Cacher: priyatno poznakomitsa ... vy govorite po-russki?

[ArtMan]

Would I drive to northeast PA in the dead of winter for Zhanna's benchmark chocolates? U-Bet I would!

-ArtMan-

[Zhanna]

ArtMan, I'm sure you're better off staying where you are this time of year!

If there's ever a benchmark event I'm able to attend, I will be sure to bring along a bunch for everyone to sample.

I currently have a raspberry gelatin benchmark chilling in the fridge. I can't wait to see how that turns out!

~Zhanna

http://surveymarks.planetzhanna.com/

[fishingdude720]

It might be kind of hard to make molds with some of the bm's because they get weather and don't always have indented letters. Most of the bm's i found are smoothed and printed on

[Wintertime]

[Rich in NEPA]

I've got mine! Yummy!!! Thanks, Z!

(Now I need to figure out how to get away with logging this as a “Find.” The coordinates might be a little off, though! )

[Wintertime]

I don't usually advocate destroying benchmarks, but I'd be happy to help get rid of some of these. :-)


Patty