Your designer has a good point. Many people prefer the more natural look of cleft face Pa Bluestone in the full color range. It is much less formal looking, and the variations of textures & colors give it a warmer, more old world look.

Thermal bluestone is a better option if you want a very smooth consistant level surface. Around a pool, where everyone is probably barefoot, there is much less risk of stubbing a toe or even tripping. The texture is a very consistant stippled surface. A link to some large pieces of thermal bluestone below:

Here is a link that might be useful: {{gwi:288645}}

As a Hardscape installer i would be more inclind to go with the regular PA flag, as it does provide more texture and colour, however the points above are also something to consider,. also be aware of teh cost, the thermal is likly to cost alot more

Stoneguy has excellent points - we actually have a secondary patio in regular PA flagstone, and even wearing shoes my kids (not to mention me) seem to trip on it every once in a while. I can only imagine how often they'd be tripping while barefoot and running (even if I tell them not to) on a wet pool deck made with the natural cleft material. Also, the stippled surface would provide a more slip-resistant surface, I would think. I'm imagining it would be slightly sandpapery. I think we're leaning towards doing the thermal, even at the higher cost, because of the safety issues. And our landscaper today told me, in a further effort to convince me to do thermal bluestone, that it's easier to lay down (we're doing it on a concrete slab) because the stone is more precisely cut and we would have smaller mortar joints, which I think would be cleaner look. He also said that the thermal bluestone would also have some color variation, just not as wide a range as the regular stuff. Would you agree with that? Ideally, they would thermal-treat the regular stuff with the full color variation and not just the bluestone, but I guess nobody does that.

Thermal finish is available in both "Blue" and "Full Color" range. There will be variations of of hues in the blue. Colors can be slate gray, blue gray, greenish gray, light charcoal gray, and variations of these. The more of it you buy, the wider the color range you can expect to see.

Full color range thermal should be bought with caution. Some producers have nice greenish brown hues intermingled with the colors above. However, many quarries use the low grade blocks of stone to cut thermal flagging. Low grade blocks have many inclusions of a black color material, in spots that range in size from 1/8" up to the size of an egg. These spots are usually refered to as coal or iron balls. When stone with these inclusions is exposed to the weather, these inclusions begin to oxidize, creating rust colored areas on the stone. These rust areas continue to grow in size over time. This lower grade multicolor thermal flagging is oftentimes available for the same price as natural cleft flagging. If you don't mind the yellow/brown stains, this stuff is a bargain.

Expect to pay about $1.50 to $2.00 more than natural cleft good quality, non-bleading full color range thermal. Expect to pay an addition $2.00 to $3.00 per sq ft over full color thermal for the premium blue thermal.

Should you decide to use the thermal for your deck, specify you want 1 1/2" thickness rather than 1". It's not much more expensive. 1 1/2" thickness is more forgiving of less than perfect installation proceedures, and less likely to pop loose from the setting bed over time.

For a nice write up about bluestone, visit the site linked below

Here is a link that might be useful: Website of Bluestone producer

Stoneguy, thanks so much for the excellent information and advice. Didn't know about the iron balls in the full color thermal flagstone. I think we'll stick to the bluestone flag because while I like the brown tones, I'm not crazy about the rust tones, especially ones that expand! And I feel better knowing that there can be color variations in the bluestone. Hopefully, that's what we'll get.

Spunky_ma_z6, never thought about the ice issue since we actually don't walk on our secondary flagstone patio that much in the winter. But we'd definitely be walking on the new patio during the winter time, and avoiding ice patches to the extent possible would be nice. Would love to see pics of your patio if you have any! Curious to see just how uniform in color your pieces are.

The stones are very uniform in color. A few "green blue" ones came in the pallets but we sent them back.

Here are some pics, but keep in mind they are "dirty"--it's a work in progress on a small city lot and nothing has been acid washed yet. Pardon the debris and lack of plantings as well---that's next!

Here is a link that might be useful: bluestone patio work in progress

Spunky, thanks so much for the pictures! You're doing a great job with your backyard and I love the patio and the little details, like the diamond pattern and the border with the darker pieces (and, even though it has nothing to do with the patio, I think your fence is beautiful!). We did a diamond pattern and border with porcelain tile in a narrow basement hall we have and it makes all the difference. You're right, your pieces do seem very uniform in color, but it doesn't seem to bother me. We would probably keep the green blue pieces, though, since we'll have a lot of patio and the color variation would help break it up. Can I ask about your acid wash comment - is that for the stone? What does that do to it?

Acid washing gets all the dirt off--for instance, what you see in my pictures looks "cloudy" or "chalky" because they are dirty with stone dust, mortar residue, and from being wiped with a used sponge. After it's washed it will be much "flatter" looking--no swirlies, no light spots, etc.

I think what you see as "dark" is actually a shadow. They are all exactly the same color. But we made an extra effort (and paid more) to get that effect.

The biggest different to me isn't the color as much as the texture--natural cleft is bumpy where the thermal is very smooth.

Will definitely make a note to self about the acid wash. Even without a border, your patio is still interesting and elegant. Thanks again for the acid wash tip!

We just had a thermal bluestone patio installed and the stone, after a few months, has weirdly begun to chip on its own and turn colors. Is this normal for thermal bluestone? When we were house-hunting, we had seen two homes that had thermal bluestone patios and thought it looked so nice that we would install one ourselves at whatever house we ended up with. Both those homes were at least a few years old and their thermal bluestone pieces seemed to have weathered well, looking smooth and dark gray, almost like granite. When we got our thermal pieces, most of them weren't as dark and had more color variation (all still bluish, though) - not sure if that means anything. All we know is that after a few months, the surface of some of our thermal bluestones are pock-marked (revealing a rust-colored pebbly interior) when they were mostly smooth before - some even have a golf ball size chunk missing - and some pieces have discolored, as you can see from the pictures below. The last picture shows the color variation that we got (you can see a few of the darker pieces that look like what we saw at the other houses - two on the left, one at the top and one long one on the right). Does anyone have any idea what could be causing this? We're worried that these problems will get worse.

http://s278.photobucket.com/albums/kk100/jerseygirl67_photo/?action=view&current=IMG_5770.jpg"; target="_blank">{{gwi:286511}}

http://s278.photobucket.com/albums/kk100/jerseygirl67_photo/?action=view&current=IMG_5771.jpg"; target="_blank">{{gwi:286512}}

http://s278.photobucket.com/albums/kk100/jerseygirl67_photo/?action=view&current=IMG_5772-1.jpg"; target="_blank">{{gwi:286513}}

http://s278.photobucket.com/albums/kk100/jerseygirl67_photo/?action=view&current=IMG_5776-1.jpg"; target="_blank">{{gwi:286514}}

Jersey Girl, What you are experiencing is a problem in the Bluestone industry called Blackjack. It happens from time to time when they quarry the stone it has veins of rust within the stone and when they saw cut and thermal the stone it can cause a reaction in the stone.

Most quarriers will see that and set the stone aside, but now and then you will have this product get into the marketplace. The only solution you have is where you purchased the stone replace the product, for it will only get worse not better no matter what they tell you.

@amok Did you end up with thermal bluestone? I am considering thermal and want to know how it worked out for you?