" Making rivers problem " Topic

I purchased two 2' square Styrofoam sheets from the very helpful Antenocitis Workshop to make a 4' long river. Having stuck the two boards together,dug out a channel and painted it a mud colour. I intend to fill it in with a clear resin. The question is, what is the best way to block up the open ends to contain the resin till it sets?.

There isnt an easy way. That's a very messy way of doing it. Best to just add layers to create a flat shine rather than attempt depth.

Is that just add layers of resin?.

I've done somewhat similar things using clear packing tape to cap the end. Depending on the resin used, weight of the resin, heat of the resin (some resin is melted to pour, some is two part with exothermic reactions), set up time, and viscosity may all cause problems with the tape though.

Flat wood or other heavy blocks at the edges to support the tape will help maintain a flat surface along the ends of the resin stream, as opposed to the tape sagging or billowing out under the weight of the resin, causing your river sections to not mate against each other.

I've also used pieces of styrene or acrylic sheet as caps for similar applications, masking the profile of the river and applying spray-adhesive to the plastic and sticking it in place for the resin application.

If you use the tape, test the resin (a few drops on a piece of tape) to see if it reacts in any way with the adhesive on the tape first. If so, you could cut a piece of tape to put on the inside face of the cap, such that the liquid resin will set up against the gloss upper surface of the tape. This will also result in a smooth clear end to the resin.

Also, check to see if the resin will exhibit much shrinkage, if so, if may contract enough when dry to pull away from the foam of to actually warp the ends of the foam upward around the stream bed.

If it does warp a little, the piece can be saved by simply shaving down the underside of the center portion of the foam, until the edges rest flat on the table. A Surform tool can be very helpful for this if it is an extruded polystyrene, as opposed to a bead board type foam.

If you build up the water by adding layers of resin (or whatever you use for the water), be sure the heat and/or any contraction of the layers during set-up/drying will not cause layers to delaminate or separate during the drying process. I saw a coworker do that with a two part clear resin many years ago.

To avoid melting the foam with the exothermic reaction of the two part resin that he was using, he poured several thin layers, allowing each to partially set-up and cool before adding the next layer. About half way through building up 1.5 to 2 inches of resin, the layers started to separate from one another, resulting in obvious air pockets between layers and some cracking through the layers depth-wise. About a $10 USDK mistake at the time.

This is how Hirst Arts does it (scroll down to Pouring and Texturing water)
link

And, I suspect, if you don't have a perfect coverage of the foam by the paint, absolute coverage – no margin for the smallest gap, you may find the resin eats away the foam and then you'll have a useless mess on your hands. I'd recommend a plaster base and repaint before pouring the resin. I could be wrong here based on other's responses – but check how the foam reacts to the resin before proceeding.

Watch this youtube video it will help…

YouTube link

Regards
James

First, as Early Morning suggests above, I strongly recommend COATING THE RIVER CHANNEL with some form of spackle or putty BEFORE pouring in the resin. I've never heard of adding resin to bare, albeit painted, foam with good results.

In answer to your original question: use a piece of hobby styrene (fancy name for plastic) and a hot glue gun. Cut pieces of plastic large enough to block the end of the channel you dug out and overlap your foam board, add a narrow bead of hot glue following all along the channel opening and press the plastic on tightly. To be extra safe you can add a piece of duct tape or two over the glued-on plastic. After your resin has set it should be easy to pop the plastic off the foam and then clean off any remnants of the bead of hot glue (better that the foam board edge was also painted to help preserve its edge).

Here in the US the companies I know of that sell this sort of hobby plastic building materials are Plastruct and Evergreen. A single narrow gauge sheet approx. 6"x12" (which will provide more than enough for your purposes) should be inexpensive at a hobby or model train or possibly arts-&-crafts store.

I use Flex Paste and then paint to coat my channels and styrene cards held on with PVA to block off the channel ends. Just be sure to pour layers of "water" no more than 1/8" at a time or it'll crack while drying. Then be quite careful removing the styrene endcaps.

Thanks guys that's been really useful. I forgot to mention I have coated the channel with plaster. I think the plastic and glue gun is the way I will go.

Good luck with your project and hope you'll let us see the results. I decided years ago to stick with acrylic gloss medium on or over the paint – and mixed with it to get tinted gloss. Works great without the challenges and hazards of resin.