The Blackwood convention is a popular bidding convention in contract bridge that was developed by Easley Blackwood Sr. It is used to explore the partnership's possession of aces, kings and (in some cases) the queen of trumps, in order to judge more precisely whether a slam (ie making all, or all but one, tricks) is likely to be possible.
Two main styles of Blackwood exist - "standard" Blackwood, and a more sophisticated variant known as "Roman key card" Blackwood, named for the Italian team that developed it. Whilst the former allows inquiry about aces and kings in general, the latter allows precise inquiry about the key cards related to a particular agreed trump suit. In both cases, an initial bid of 4NT (No trumps) is commonly used as the conventional bid to ask partner about their high cards.
When this convention is in force, a bid of 4NT (No Trump) asks the partner to provide information on the number of aces in his or her hand (as long as the previous bid is not 1NT, 2NT, or 3NT). With no aces or four aces partner replies 5♣; with one ace, 5♦; with two aces, 5♥; and with three aces, 5♠. The asking bidder usually has one or two aces, so it is easy to discover the partnership's combined assets. A continuing bid of 5NT asks for kings with the replies following the same pattern. However, asking for kings tends to confirm that your partnership has all the aces and the responder may simply bid the slam at the seven level if he has an appropriate hand.
The responder should not count a void as an ace. Eddie Kantar recommends bidding the void suit at the 6 level with three aces and a void and 5NT with two aces and a void.
Although alternatives to the Blackwood convention exist (e.g. the Norman four notrump convention), virtually all bridge partnerships deploy a variant of the Blackwood convention (see below) as part of their slam investigation methods.
Roman Key Card Blackwood (RKCB)
In modern times, a system called Roman Key Card Blackwood (RKCB) has largely replaced the original system, at least among more advanced players. It originated from Roman Blackwood (see below). The king of trump is included as a control or a "key card"— in effect, as a "fifth ace"— and so more information is gained. The responses are basically the same as for Roman Blackwood, but with five "aces" in play, and additionally queen of trumps:
|5♣||0 or 3 key cards|
|5♦||1 or 4 key cards|
|5♥||2 of the 5 key cards without trump Queen|
|5♠||2 of the 5 key cards with trump Queen|
Some players also choose to use the club response to show 1 or 4 and the diamond response to show 3 or none; this is referred to as "1430" while the above version is "3014".
As with Roman Blackwood, for the ambiguous answers in the minor suits the asking partner can almost always work out which it is by looking at the controls in his or her own hand and by analyzing the bidding. The response of five key cards does not exist, as it is simply forbidden for the partner lacking any key card to query Blackwood (see below).
If partner gives a minor suit response to the RKCB 4NT inquiry, the inquiring partner may still determine if his side holds the queen of trumps. Bidding the next suit up from the 5-level minor suit response is a "queen ask" for the queen of trump. Bidding the agreed trump suit at the next available level denies holding the Queen. All other bids show a holding including the Queen, and give other information about King holdings.
All the foregoing bidding is predicated on the assumption that a trump suit has been agreed upon. Without trump agreement, the last suit bid before the 4NT bid is considered to be the agreed trump suit for responding purposes. When No Trump was the last bid made, 4NT is considered to be a quantitative raise and invitational to a small slam. Therefore a bid of 4♣ (Gerber) is used in many partnerships to ask for aces in no trump sequences.
A variation of the standard Blackwood convention, known as Roman Blackwood, was popularized by the famous Italian Blue Team in the 1960s. In Roman Blackwood, the responses are even more ambiguous, but more space-conserving. The basic outline of responses is:
|5♣||0 or 3 aces|
|5♦||1 or 4 aces|
In practice, the ambiguity is unlikely to occur, as a strength difference between hands with 0 or 1 and 3 or 4 aces is big enough that it can be established in previous rounds of bidding. In other words, a partner who has previously shown e.g. 12-15 range of high points is unlikely to hold 3 aces for his bid, etc.
Even Roman Blackwood convention has several variations, revolving around 5♥ and 5♠ responses. In all variants, they denote 2 aces. One variation is that 5♠ shows extra values, while 5♥ does not. In other variations, responses 5♥-5NT denote specific combinations of aces (same color, same rank, or "mixed").
If the querying partner ascertains that all aces are present, he can continue as follows:
- 5NT is a Grand slam force
- The first available bid which is not the agreed suit is the Roman Blackwood for kings. The partner responds stepwise, as above.
"Kickback" is the variant of RKCB devised by Jeff Rubens in accordance with the Useful space principle. The step responses are the same as in RKCB, but the ask is not necessarily 4NT. Instead it is the 4-level bid immediately above the agreed trump suit, i.e.:
|4♦||RKCB for clubs|
|4♥||RKCB for diamonds|
|4♠||– RKCB for hearts|
|4NT||RKCB for spades|
Kickback has the advantage that it saves bidding space and, especially for minor-suit fits, provides safety at the 5-level if the required keycards are missing. Since the Kickback bid would otherwise be a control bid, 4NT is usually substituted as the control bid in that suit (e.g., 4NT is a control bid in hearts if the agreed trump suit is diamonds). The drawback is that in unpracticed partnerships there can be confusion as to whether a bid is Kickback, a control bid or preference for a different strain:
East intended 4♥ as Kickback, but West thought it was secondary support for hearts, and decided to pass with minimum values. As result, a reasonable grand slam in diamonds was missed.
An established partnership might have agreed that as hearts were not supported after opener's rebid, 4♥ cannot possibly show support, and must be ace asking in diamonds.
"Redwood" is a variation of Kickback, in which the kickback principle is used only when a minor suit is trumps. The name comes from the fact that the resulting ace/key card ask will be a red suit, as follows:
4♦– RKCB for clubs
4♥– RKCB for diamonds
Using "Redwood," the ace/key card ask of 4NT is still used when the trump suit is a major (hearts or spades).
"Minorwood" is a variation of Blackwood, in which the minor suit which the partners agree will be trumps is itself used as the ace/keycard ask. The ask will be at the four level. Hence:
4♣– RKCB for clubs
4♦– RKCB for diamonds
Exclusion Blackwood or VoidwoodThe Bridge World, May 1981 Volume 52, Number 8, by Ron Gerard</ref>. was devised by Bobby Goldman as an attempt to resolve the situation when the Blackwood-asker has a void. In that case, he is not interested in the partner's ace in the void suit, as he already has the first-round control; partner's ace would present a duplicated value in that case. It should be noted, however, that many players, even experts, refuse to play Exclusion Blackwood because of the potential disaster of forgetting the agreement.
It is usually played as the Roman Keycard Blackwood, with only four keycards: the three Aces outside the void suit and the King of trumps. However, the asking bid is not 4NT, but the void suit— Voidwood is made by jumping on level 4 or 5 in the void suit after a fit has been found, for example:
Bids of 5♣, 5♦ and 5♥ present a Voidwood, denoting the void in the suit bid and asking for other keycards. The responses are, as in RKCB:
- 1st step – 0 or 3 key cards (1 or 4, if playing 1430)
- 2nd step – 1 or 4 key cards (0 or 3)
- 3rd step – 2 key cards without trump queen
- 4th step – 2 key cards trump queen
The Blackwood convention is not without problems. When the Blackwood bidder has a void, he is not able to tell whether partner's ace is in the void suit (where it would not be of great help) or in a side suit (where it would be very useful.) For this reason cue bidding to show aces is a superior method with hands that contain a void. In fact, most beginner-level players misuse this convention; they ask for aces when they really need other information from partner.
Beginners—and even more advanced players—often fail to comprehend the fundamental purpose of the Blackwood convention. They believe—incorrectly—that the convention is designed for the purpose of ascertaining if the partnership holds all four aces. In fact, the purpose of Blackwood is fundamentally to determine if the partnership is missing two or more aces. If the partnership is missing only one ace, then contracting for 12 tricks may still be reasonable, assuming that the partnership resources are sufficient to capture this many tricks.
Blackwood should not be used when the information gleaned will not answer the question that needs to be answered. A simplified, but instructive, way to think about Blackwood is this: "I am concerned that we may lose the first two tricks, if we bid a slam. I can use Blackwood as a kind of insurance policy, to guarantee that this will not happen." But Blackwood will not help if, due to the structure of the hands, there are multiple ways to lose the first two tricks. It only helps, for the most part, if the exclusive risk of losing the first two tricks is due to the opponents' holding two cashable aces. Obviously, the opposition might hold the ace and king of a side suit, and could bang those tricks right down, resulting in an immediate set.
Thus, a player should use Blackwood only when he can ascertain that the partnership holds at least second-round controls in all suits (kings or, if a suit fit is found, singletons). Thus, a Blackwood query by the player holding two quick losers in a side suit is a wild gamble, as it is still possible that the suit is not controlled by an Ace or a King.
For the same reason, it is generally wrong to use Blackwood with a void. (This is not always true, but the rule of thumb is: Don't use Blackwood with a void unless you are absolutely sure you know what you are doing, and why you are doing it. If you don't understand why it is correct, in a given case, to use Blackwood with a void, then it's very likely that its usage will be incorrect.) You may be missing two aces, but your void may compensate for the lack of one of the enemy aces. Thus, Blackwood will not tell you what you want to know: Are we at risk of losing the first two tricks? If your side has two aces and a void, then you are not at risk of losing the first two tricks, so long as (a) your void is useful (i.e. does not duplicate the function of an ace that your side holds) and (b) you are not vulnerable to the loss of the first two tricks in the fourth suit (because, for instance, one of the partnership hands holds a singleton in that suit or the protected king, giving your side second round control).
Other problems can easily occur when clubs is the agreed upon trump suit. The reply to Blackwood could take the partnership past their agreed suit and going to the next higher level may be one trick too high. The adage is 'don't use the convention if there is a possibility you won't like the reply.'
A further problem occurs when, after hearing his partner's response, the player who bid 4NT wants to stop in 5NT — as this is a forcing bid asking for Kings. The usual situation here is to bid a previously unbid suit instead (if there is one available) - your partner should recognise that this cannot be a genuine bid and corrects to 5NT.