Amy, I don't use perlite often, but I visited friends in Europe last year and in this May again, I wanted to make some planters for them. The perlite there is almost powder. Last year it didn't set for 3-4 days. This year I used different ratio( plus sand and peatmoss ), SAME PROBLEM! But maybe the cement is different too.

i have never had any set-up problems using perlite, but then again, I never pulverized it or used a powdery form of it. Could it be the powdery perlite is giving you trouble? It shouldn't be. Perlite is just a volcanic rock. Has nothing in it to slow down the curing of the crete. Only thing I know that slows down the curing is the temperature and if any carbohydrates (aka sugars or starches) get into the mix.

Gottatufa,

I'm thinking you may be right about the powder. Maybe I should have sifted out the powder before I used it, but that sure would make for a lot of waste. Or maybe I should have sifted the perlite and then put just the large pieces in the blender??

Amy

Morning to you!I've been using what Grace Industries calls their "cryogenic"quality of perlite-very fine bead to it.I'm using it in a 1:1:2 combo(cement/sand/perlite)in my masks,some of them weighing upwards of 35 pounds.I've popped them from their molds in 24 hours,cured them for the usual and hung them up.
And no problems with the mixture.Using either water or admix.
The finer bead seems to give a smoother surface.
My 2 cents CDN worth!

Thanks for the tip Rick. I will try to get some of that.

Amy

I have used powdered perlite that I ground up myself and didn't have a problem, but it was a much smaller percentage. I used 1 cement, 1 sand, 1 peat moss, and 1/3 ground perlite. . . trying to make things lighter. I don't like using perlite to carve in. Where can you get the beaded perlite?

Look up "Grace Construction Supplies" or "Zonolite".That should track you to a local supplier.Any specialty supply business(for concrete,masonry)should have it or be able to get it.I found a supplier in Burnaby,BC that had a dozen bags(I took a couple).The manufacturer also has specialty vermiculite as well.As to ratios..this stuff is VERY fine.The results are that My biggest mask would easily weigh over 70 lbs,but I've got it down to about 35 lbs or so.Still damned heavy.I use an insert of aircraft cable to hang it from!

I use powdered perlite alot and have noticed no difference in the setting times. I use a recipee of 1 sand, 1 powdered perlite, 1/2 fine vermic, 1 peat, 1 port. Perlite is a bit tricky to work with only in that it blows all over the place. I use a mask and sealed goggles when mixing.
Someone mentioned here that you can use 2 parts lightweights (by volume) to replace 1 part sand. I have yet to go that far though.
GB

Rick, I got the perlite from Home Depot, gardening section.All the planter mixes contain perlite, vermiculate, to hold water better and make it lighter.

Industrial perlite isn't found at HD.I'm talking BIG bags for about 24 dollars(can't remember the volume,bag stands about 3-4 ft tall)in a variety of bead size.Because of its volcanic origin,I wouldn't want to use my blender on it to reduce the particle size.Somebody else's blender,sure.

Rick HD does or did have those HUGE bags of course only perlite for under $20.
I bought my first one there.
I don't recall the size either. HUGE, many many litres.:)

The course stuff does have it's uses for a rustic appearance but like you I prefer the fine stuff for most stuff.

Running chunks of that white bead styrofoam throught the blender, it breaks it down into the individual beads.
You want some light weight tufa try those.
I wish I could buy these 1/8 inch sized styrofoam beads in bulk.

What about bean bag chair filler?

Mabel

Here is a link that might be useful: bean bag chair polystyrene beads

When I started on Hypertufa,I looked thru web info about perlite.There are both horticultural and industrial kinds.I've only ever used industrial,as was recommended at the time.The stuff I'm using now is as fine as sand and gives a nice finish to the product.I've used the chunkier stuff,prefer this.
For the info of those on the West Coast,BC,the company I dealt with is Pacific West Systems Supply Limited,with locations in Kelowna,Burnaby,Maple Ridge, Langley,Squamish and Abbotsford.Their product code is 0429700.
Cheers

Mabel the virgin stuff is basically what I get out of the blender. Nice BB sized pieces.
But the price they want is too high for me.
I just need a bigger blender.:)

But I'm going to keep my eyes open for those bean bag chairs at garage sales.

I, too, had trouble when I tried using the agricultural stuff instead of the vermiculite mix I'd been using. It never did set right and stayed crumbly. I already had bought it when I saw big bags where I purchased the white portland cement. Also, those big granules were too coarse IMO. I'd originally planned to try and emphasize this and do a faux granite look, but ended up covering up the damaged pots with a sand/portland mix and covering these with wet leaf castings.

Back to my original comment, the first one on this posting, the powdery perlite I had the problem with, came from the building supply store, not gardening. But, as I mentioned, I never worked with that cement and the climate is much drier than here in Beautiful British Columbia!

Andrea

Thanks to all for your comments. Seems I'm not the only one who has had some problems with perlite. Others seem not to have any problems at all. It's a puzzle. Guess I'll have to do some serious experimenting with the perlite to see if I can determine the problem.
The projects that started this post have finally cured to a point that I normally get within a day or two, but it has taken them about 10 days and it has been quite warm to hot here. Even though most of the water has evaporated, I can still scratch them with my fingernail, and they are a bit crumbly. I can chip off little pieces with my fingernail.
I really don't like the crumbly part, I could live with the slow curing.

Again thanks for all your comments.

Amy