Strengthening Limestone Plates

[Goldfinger]

Hello

 

I have some thin limestone plates that contain fossils. Some are only 1/4 inch thick.

 

I would like to strengthen them with a plaster backing. Is plaster of paris the only ingredient you use or are other strengthening or adhesive agents used? Perhaps to help attach the plate more firmly?

 

Help would be appreciated

 

Thanks 

[Fossildude19]

Moved to FOSSIL PREPARATION. 

 

@Ptychodus04  @RJB

[Troodon]

Another option I've seen is using backing boards like 1/8" plywood epoxied to the back

[digit]

Indeed. I've seen this sheets of fossils laminated to plywood with epoxy which would likely give the maximum of rigidity. If you choose to go the plaster route, I'd strengthen that with either sheets of burlap (which is how we make plaster jackets in the field) or possibly fiberglass mesh tape. You can find such tape in your local home improvement store where the joint compound and tools and supplies are found for joining drywall.

 

If you take photos along the way and write-up a report on your chosen method of stabilizing this thin fossil, it would make for an informative post for those who search for similar solutions in the future.

 

 

Cheers.

 

-Ken

[Ptychodus04]

The method really depends on your intent for the specimens. I've made plaster and burlap backings for fragile specimens during prep. You can also use fiberglass. If you just want to keep them from breaking, I would go with the plaster 1/2 jacket. It gives enough stability to the specimens to keep them from breaking but it isn't the most esthetically appealing. Backing with plywood is more eye friendly but permanent. I would use 1/2" plywood and adhere with a slow set epoxy. Use Bondo to fill in any gaps on the edges between the matrix and plywood, sand, and paint the edge to match the matrix. This provides stability with a good look and also allows for easy mounting on a wall if desired. 

[Goldfinger]

Plywood sounds nice but the back isn't completely flat or level. Some areas are 1/2 inch thick. Others are 1/4 inch thick. Would I have to sand the back until level...then glue and attach the plywood?

 

[digit]

If there are any deep holes or pockets, you could lie the plate with the back side facing up and mix up a batch of longer setting (not 5-minute) epoxy to fill in the voids. Alternatively, you could mask off the sides of the plate and protect the face with some plastic sheeting or aluminum foil (taped around the edges). You could then put a fair amount of epoxy (or other glue like Liquid Nails) and press the plywood backing in place. Clean-up the glue squeeze-out along the sides and you should have a really secure attachment.

 

 

Cheers.

 

-Ken

[RJB]

  I'm only speaking for myself here.  I like to use Dura-Rock.  It comes in different thicknesses, I use mostly the 1/4 and 1/2 inch depending on the size of the slab I want to back.  Years ago I was using plywood and one time it warped making the this Green River slab warp with it.  Thats when I started using Dura rock.  Its loaded with a fiber and does not expand, contract or warp.  I also use silicone for the glue.  This, applied correctly will take care of those gaps you are talking about.  If you live in a high moisture area, then I would use Silicone Type 2.  This wont mildew.  When I started working with the broken fish slabs from Lebanon, all the pieces were of different thicknesses and sometime buy quite a bit, 1/2 inch sometimes and more.  With this problem after I glued the 'high' parts with silicone, I used Rock-ite mixed thin enough to pour into the crack/s while the slab is standing on edge.  There are lots of different things you can do, just have to find one your happy with.  Good luck

 

RB

Here is a fish slab that was in a few pieces.  Glued onto Dura Rock with silicone

 

After sanding into a perfect oval I will fill the crack between the rock and the dura rock with Rock ite an sand.  Will look almost perfect.

 

Here you can see the differences in thickness of the pieces of rock and how Im filling up the spaces.  Once trimmed up it will look purty good. 

 

 

 

[digit]

Excellent advice!

 

 

Cheers.

 

-Ken