Polling You #44: Slam Bidding – Blackwood, Day 4, February 23, 2011

Blackwood Slam Bidding Convention in Contract Bridge

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Bidding slams are exciting – never a dull moment.  Back in the late 1930s, Easley Blackwood came up with a conventional bid to ask partner to disclose the number of Aces.  Being a manager for an insurance company and wanting to capitalize on his newly invented bid, Easley called his convention “Wormwood” (not wanting senior managers to think his card play was risky). 

Easley also applied for a patent on Wormwood.  But the name never stuck and the patent office scoffed at the idea of patenting anything to do with Bridge.  Fortunately, his convention was loved by many who simply called his treatment the Blackwood convention.  And so Easley’s Blackwood bidding system has become the beloved slam asking bid over the last 70 years.

Slam – Three Possibilities

1. Classic Suit Slams – Majors, Minors
Use 4 Notrump “Blackwood” to check for Aces

2. Distributional extra long suits and two-suited Slams – Majors, Minors
Use 4 Notrump “Blackwood” to check for Aces

3. Balanced Slams – Notrump
Use 4 Club “Gerber” to check for Aces (more in next lesson)

Blackwood Prerequisites:

1. No worthless doubleton or void (instead use control bidding)

2. Suit Agreement (not Notrump contract)

3. One player jumps with self-sustaining suit (usually a major suit)

4. Small slam
a. 33+ distributional points
b. 12 tricks
c. 3-4 Aces or controls (singleton/void)

5. Grandslam
a. 37+ distributional points
b. 13 tricks
c. 4 Aces or controls, 3-4 Kings or controls (singleton/void)

The purpose of the Blackwood convention

1. Explore small slam
a. Bid 4 Notrump to ask
b. Used to ensure sufficient Aces (3-4 or controls/shortness)

2. Explore grandslam
a. Promises Aces or all first round controls (void)
b. Follow-up bid 5 Notrump to ask
c. Used to ensure sufficient Kings (3-4 or controls/shortness)

Examples of Blackwood:

1H – 3H; 4N

1C – 1H; 1S – 4S; 4N

1D – 2H; 4N

2C – 2D; 3S – 4N;

Blackwood Continuation Bids:

1H – 3H; 4N – 5H; 5N   With all Aces/controls, King ask

1S – 3S; 4N – 5C; 5S      Not enough Aces, signoff in 5S

1C – 3C; 4N – 5D; 5S – 5N    Not enough Aces, 4S (new suit) forces 5N “to play”

Examples of Non-Blackwood Bids:

1N – 4N;   Quantitative slam invite – bid 6N or pass with minimum

1N – 4C;    Gerber Ace-asking over Notrump

1N – 2C; 2S – 4N   Quantitative slam invite, pass or bid 6 Notrump

1N – 2C; 2S – 4C    Gerber Ace-asking over Notrump

Blackwood Responses after 4 Notrump, as 1H – 4N;

5C = 0 or 4 Aces
5D = 1 Ace
5H = 2 Aces
5S = 3 Aces

5N = Even # of Aces and useful void
6x  = Odd # of Aces and useful void (in lower ranking suit than trump agreed suit)

Blackwood Responses after 5 Notrump, as 1H – 4N; 5C – 5N;

6C = 0 or 4 Kings
6D = 1 King
6H = 2 Kings
6S = 3 Kings

Slam Bidding Tips:

1. Relax, take a breath, enjoy the moment

2. evaluate, Evaluate, EVALUATE !!!

3. “The one who knows, goes!” (Blackwood, Slam)

4. When in doubt, invite – your partner will help

5. Know when to instead bid controls

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Warm Regards,



  1. BridgeHands says:
    Hello Pollsters,
    Slam bidding can be a real joy, especially having fun tools like the Blackwood convention. And now that we’ve covered exceptions when to use control bidding, let’s see how we scored this poll:
    One-half of our pollsters agreed both of these candidates applied to Blackwood:
    After 4N ask, with 2 Aces respond 5 Hearts
    After 4N ask/response and 5N rebid, with 3 Kings respond 6S
    Regarding adding this addition to the above, a smaller 37 percent were in agreement:
    After 4N ask, with 2 Aces and a useful void bid 5 Notrump
    While responding to Blackwood with a void is not a common occurence, it’s a good idea to have some kind of agreement in place, and this is the standard treatment. So even with zero Aces and a useful void, the responder can bid 5 Notrump to signify an even number of Aces (0 or 2). Of course, if the void is in partner’s initially bid suit, all bets are off and we would forget about the fancy treatment to show a void – showing a void does not apply when partner shows appreciable length in the suit.
    Happy Trails,
  2. n74tg says:

    The download link appears to be busted for this Poll; also true for Polls 47 and 51.

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