dark grey… almost black… are easy to get… but to get jet black… black is black … thats a feat…
started at 9am yesterday… measured…built the molds… mixed the mix and cast them… only 3 countertops in this kitchen but i knew they needed to be cast from one batch/mix only about 18ft total… but one goes over a lazy susan/corner … one has a sink cast in place… and one is just a slab… i cast them face down but i still like a nice smooth finish on the bottom side… so hit the last steel trowel to it @ 5pm (finished the molds @ 1:30pm
I used a portland rich mix with black iron oxide and powder carbon black… I use a mix that is wetter than what many use but i use more portland… but… black is some nasty stuff… I work slow and clean… and it still seemed far worse than any other color i have ever cast…
i can cast up to 30ft on my casting table … 2 16″ I-beams with 5″ flange 17″ apart giving me 27″ of steel support (they are bridged with 2″ angle iron) i have them about 20″ off the ground i just place my molds/forms on top of them.,..
some people keep the concrete in the mold for 4-5 days… I’ll take these out monday and cast another kichen using the same basic forms…
fun for me 🙂
p
Replies
Sounds like a car building table to me.
Guess you found your carbon black?
Joe H
it's much like the surface plates we use to build race cars on... yes found the carbon black at an industrial paint supply house... $5 lb think i last paid 70cents lb 5-7 years ago... used 2% ie 2lbs carbon black to 94lbs portland and i think that might be too much
p
Edited 6/7/2009 6:10 pm ET by ponytl
I go up to a max of 8% powdered pigment by weight.
in yellows... browns... and one green one i used what seemed like 10% pigment... and yes those colors are nasty and get everywhere also... and they seem to be on par weight wise with portland... but carbon black... well a 25lb bag is larger x2 than a 92lb bag of portland... I don't know the science of it but it takes ALOT to make 5lbs like almost a 5gal bucket full... and it's fine fine fine... I don't know the partical size but far finer than any pigment i've ever used...
btw i flipped one 42" top out of it's mold today... I'm real pleased... on the next set i will not use caulk on the joints... i have them so tight anyway i don't see the need and i'll polish the edges anyway...
again i cast the sink in place... was an undermount sink... which was a first for me... i cast top mount sinks in place all the time... curious how this one will turn out... if not good then i'll cast the next one like it and center the sink in the top... just requires a 3/4" buck in the mold
thanks for your continued input on this subject
p
Be careful not to get any of that fine stuff in your camera, it'll ruin it & you won't be able to post any more pictures.
Joe H
I had to reply...
Lol.
Great tip..Remodeling Contractor just on the other side of the Glass City
oy vey, I finally saw one of his pictures:.
.
.. . . . . . . .
That was great. LOL
when the h are you gonna get a camera??
"When the spirits are low, when the day appears dark, when work becomes monotonous, when hope hardly seems worth having, just mount a bicycle and go out for a spin down the road, without thought on anything but the ride you are taking." — Sherlock Holmes, 1896
For "black" black I'll use liquid and solid colorants. Pea gravel as the aggregate can lend a mottled look to the slab with slight variations in shade, which is normally desired. But for a solid color I'll usually leave out the stone and just use portland, sand, and colorant.
And yeah, isn't amazing how dirty black can be? A little stray black can dirty a lot of space in no time at all.
A salesman once told me the dirtiest place he ever visited was a plant that made toner for photocopiers. The stuff was everywhere.
kinda like a machine shop. Oil cutting lubricant on everything/everywhere
"I'll usually leave out the stone and just use portland, sand, and colorant."
I've done maybe 6 or 7 counters and been tempted to skip the aggregate for a few reasons but haven't had the nerve... can you splainst a bit about that?PaulB
http://www.makeabettertomorrow.com
http://www.finecontracting.com
When I first started doing these tops about 15 years ago, I tried everything. This is before I ever heard of Rhodes or Chang. Or concrete countertops, for that matter.My inspiration was a little excess concrete that I had dumped into a drywall bucket after a small pour while building my own house. A couple days later when I flipped the bucket over to pop out the slug of waste concrete, what caught my eye was the perfect smoothness of the slug.Couple that with the $$$$$ quote for slate countertops in my own yet-to-be-finished kitchen, and thus the inspiration to experiment. Technique, mixes, form materials, etc. Add in an adventurous wife who was wiling to trade slate for concrete, and off I went.I'll preface this by saying I always cast inverted. I always use gloss formica to line my mold. I could reuse the same formica several times. I'd buy damaged sheets at the box stores for $10 each. When I pop my slabs out of the mold, they are glass smooth with a mirror like gloss finish.With all that preface out of the way......if I add pea gravel as the aggregate, I get a slightly mottled look to the surface of the countertop. Hard to describe, but there's a bit of visual texture to it...slight variations in color shade across the slab. Very earthy, very natural. Love the effect. The top is still glass-smooth, but the visual mottled texture is there....if I just use sand and portland, with no stone in the mix, I get a very monochromatic looking slab. No variations in color, just a nice even monochromatic color across the surface.
I do it the same way, but have never omitted the stone. I was always under the impression that there's too much loss of strength. Any thoughts or experience with that?PaulB
http://www.makeabettertomorrow.com
http://www.finecontracting.com
Never had a problem. I think the longest slab I've ever done without stone was around 18'. A big concern going into that one was shrinkage cracks.But yup, with it being "mortar" instead of "concrete", proper water portioning as well as plasticizers and admixes can help improve the final product.The less stone you use, the more you need to be concerned with shrinkage cracks.Way back when I did full thickness sand/cement slabs and compared them to slabs where the bottom 2/3rds was sand/stone/cement and the upper third was sand/cement.Totally nonscientific comparison. But the results gave me the confidence to use full-thickness sand/cement.
Real interesting... thanks. Any tips on what admixtures you've used and how you determine proper water content?PaulB
http://www.makeabettertomorrow.com
http://www.finecontracting.com
I haven't done a slab in a few years. I'd have to go dig my notebooks out of the basement. I used to get my stuff from a supply house in Westbrook CT. Then I had to transition to mail order when they stopped carrying some product.And "proper water content"? Yeah, as little as possible!<g>
LOL... and some eye of newt? Bat wing? (almost wrote that as bat wong :S)
PaulB
http://www.makeabettertomorrow.com
http://www.finecontracting.com
I was tempted to urinate in the mix of one guy's slab. But then I settled down and realized that thinking about it was smarter than actually doing it.Opportunity lost.
I once tossed a 10 lb bluefish into someone's air handler... before a long weekend. They were unbelievably obnoxious "neighbors" at my old business. Sighhhhhhhhhh... that felt good.PaulB
http://www.makeabettertomorrow.com
http://www.finecontracting.com
I don't laugh often when reading stuff online, but I just did!
Took a look, the plasticizer was Supersizer from Fritz-pack, I'd get boxes that contained small bags already portioned. The admix I think was called polyplex, but I don't remember if that's the company name or the product name. I got that in 55 gallon drums. It's similar to a regular latex poly admix that's used to modify thinset.When doing the sand/portland slabs I'd load up on the admix. It really helps retain moisture during the cure which helps eliminate shrinkage cracks and pumps up the end strength of the slab.
Thanks, I'll look for it next time. Funny, I felt the same way as you guys. My first counter was humungous, and cast in place. It was covered with plastic for a week or so but I kept peeking under the edge. The first one I cast inverted and turned out I was like a little kid on Xmas... it really is a riot to see what lowly concrete can be.PaulB
http://www.makeabettertomorrow.com
http://www.finecontracting.com
I do close to what you do... except the guy next to me installs signs and many time they have new sign faces that have never been installed for any number of reasons... so i end up with 3-4ft wide x 6 - 12ft long sheets of lexan... one side is always good... and super slick... and FREE...
I use super white "golf course sand" it's the best sand i can get... I do use a stone in my mix also... but not alot... the stone i use is a crushed white rock like a number 10 or something... nothing bigger than a dime most smaller... very jagged and white and it's porious.. i can stain it...
my mix is wetter than most... standard for me is a full fix in my mixer... in 5 gallon buckets... 4-5 sand 2 rock and a full bag of portland... and water... for my black i used a bit of black iorn oxide to color my mix water (just seemed like a good idea) and added about 2lb of carbon black to that... put about 2.5 gallons of the black water in my mixer added 1 bucket of rock and the carbon black... let that mix while i got the rest ready... I have a scoop bucket i built for my bobcat that i load the rest in ...sand rock & portland.... i then dump that into the running mixer... added more water.... let it mix... then the mixer gets dumped back into the scoop bucket... and i drive the mix to my forms... the scoop holds a full mix... enough to do about 16-18ft of counter top...
mine also come out glass smooth... I think it was you that turned me on to the hammer drill for the vibrator... best vibe by far of all the things I've tried...
about the best i can do is leave em in the mold for around 48hrs... hard for me to wait that long
P
Sounds like you have the system down pretty well.For earthy colored slabs or somewhat muted colors, I'll use regular sand and regular portland cement.For bright or really pure colors I'll go with white silica sand and white portland cement. That really lets the pigment take over. You can get neon colored slabs with that.It's funny, I had the same problem. whenever I tried a new technique or a new color I really had a hard time waiting to pop the slab out of the form.
what are the molds made of and how do you radius the drip edge, it's hard to see in the pictures
.
.
. . . . . . . .
if you look at th pics it's all very clear :)
my computers resolution doesn't pick them up...:)so you made your molds ? I kind of like the idea of concrete, but so far no one around these parts does them.
.
.. . . . . . . .
Sounds like fun! =)
I always wanted to try my hand at casting a concrete counter, still waiting the opportunity. If and when that day comes along I'm gonna have plenty of questions for ya.
~ Ted W ~
Cheap Tools! - MyToolbox.net
See my work at TedsCarpentry.com